feat(water-log): Smartsheet sync integration

Per-brand Smartsheet integration that pushes new water_log_entries to a
configured sheet. Config UI lives at /admin/water-log/settings.

Database (0093_water_smartsheet_sync.sql):
- water_smartsheet_config: one row per brand; AES-256-GCM encrypted API
  token (BYTEA), sheet id, column mapping JSONB, sync_frequency
  (realtime | every_15_minutes | hourly), enable flag, last-sync
  metadata. RLS via existing current_brand_id() pattern.
- water_smartsheet_sync_queue: one row per entry awaiting sync;
  tracks status / attempts / exponential backoff. UNIQUE(brand_id,
  entry_id) for idempotent enqueue.
- water_smartsheet_sync_log: append-only audit of every sync attempt
  (success or failure); backs the Recent Activity panel in the UI.

Server:
- src/lib/crypto.ts: AES-256-GCM encrypt/decrypt + token mask helper.
  Reads SMARTSHEET_TOKEN_ENC_KEY. Throws on missing/wrong-size key.
- src/lib/smartsheet.ts: typed REST wrapper (no SDK; the official
  smartsheet npm has Node 22 compat issues). getSheetMeta, addRow,
  findRowByColumn + typed SmartsheetApiError.
- src/services/smartsheet-sync.ts: syncEntryToSmartsheet (one entry),
  drainSyncQueue (batch with backoff), runScheduledSync (cron entry).
  Sequential processing stays well under Smartsheet's 300 req/min.
  Max 5 attempts, then row stays 'failed' permanently.
- src/actions/water-log/smartsheet.ts: 6 server actions. Token never
  returned in plaintext — UI gets maskedToken only. Permission check
  matches the rest of the water-log module (can_manage_water_log).
- src/app/api/water-log/smartsheet-sync/route.ts: POST cron route,
  bearer auth via SMARTSHEET_CRON_SECRET (falls back to CRON_SECRET).
  Optional {brandId} body for manual retry.
- vercel.json: added */15 * * * * cron entry. Single entry covers
  both 15-min and hourly frequencies (route filters per-brand).

UI:
- src/components/admin/water-log/SmartsheetIntegrationCard.tsx:
  self-contained client component with useReducer. Sections: enable
  toggle, sheet URL/ID + API token + Test Connection, sync frequency
  radio group, column mapping dropdowns (populated after Test),
  Recent Activity panel.
- src/app/admin/water-log/settings/page.tsx: mounted the card as new
  '§ 05 — Integrations' section after the existing admin-PIN settings.
  Card takes brandId as a prop (CLAUDE.md 'Brand ID Threading').

Hooks:
- src/actions/water-log/field.ts::submitWaterEntry: calls
  triggerSyncForEntry(brandId, entryId) in a fire-and-forget void
  after the entry insert. Sync failures NEVER bubble to the field
  worker.

Env vars (.env.example):
- SMARTSHEET_TOKEN_ENC_KEY (REQUIRED, 32 random bytes base64)
- SMARTSHEET_CRON_SECRET (optional bearer)
- SMARTSHEET_SYNC_TIMEOUT_MS (optional, default 8000)

Deploy:
1. openssl rand -base64 32 → SMARTSHEET_TOKEN_ENC_KEY in .env.local
   AND Vercel dashboard
2. npm run migrate:one 93  (pushes 0093_water_smartsheet_sync.sql)
3. Push triggers .gitea/workflows/deploy.yml

Rollback: remove cron entry, DROP the 3 tables, revert field.ts +
settings page hooks, git revert the merge commit. See MEMORY.md
for full rollback story + sharp edges (no key rotation, slug URLs).

db/migrations/0093_water_smartsheet_sync.sql

@@ -0,0 +1,188 @@
+-- ============================================================================
+-- 0093_water_smartsheet_sync.sql
+--
+-- Adds per-brand Smartsheet integration for the Water Log module.
+--
+-- Three tables:
+--   1. water_smartsheet_config      — one row per brand; encrypted token,
+--                                     sheet id, column mapping, frequency,
+--                                     enable flag, last-sync metadata
+--   2. water_smartsheet_sync_queue  — one row per water_log_entry that
+--                                     needs syncing; tracks attempts + status
+--                                     for retry / observability
+--   3. water_smartsheet_sync_log    — append-only log of every sync attempt
+--                                     (success OR failure) — backs the
+--                                     "Recent Activity" panel in the UI
+--
+-- Security:
+--   - API token is AES-256-GCM encrypted at rest using a key from
+--     SMARTSHEET_TOKEN_ENC_KEY. The token NEVER leaves the server in
+--     plaintext via any server action / API response.
+--   - All tables brand-scoped via the existing `app.current_brand_id`
+--     GUC + `current_brand_id()` function (see 0001_init.sql).
+-- ============================================================================
+
+-- ── 1. Config table ────────────────────────────────────────────────────────
+
+CREATE TABLE IF NOT EXISTS water_smartsheet_config (
+  brand_id UUID PRIMARY KEY REFERENCES brands(id) ON DELETE CASCADE,
+
+  -- The numeric Smartsheet sheet ID (not the share URL).
+  -- UI accepts either form and parses to numeric here.
+  sheet_id TEXT NOT NULL,
+
+  -- AES-256-GCM encrypted API token (stored as BYTEA so we can store
+  -- raw bytes, not base64). Use the helpers in src/lib/crypto.ts.
+  encrypted_api_token BYTEA NOT NULL,
+  token_iv BYTEA NOT NULL,         -- 12 random bytes per encrypt
+  token_auth_tag BYTEA NOT NULL,   -- 16-byte GCM auth tag
+
+  -- Maps our internal water-log fields → Smartsheet column IDs.
+  -- Shape: { entry_id: string, logged_at: string, headgate: string,
+  --          measurement: string, unit: string, irrigator: string,
+  --          notes: string | null }
+  -- `entry_id` and `logged_at` are required (used for dedup).
+  column_mapping JSONB NOT NULL,
+
+  -- 'realtime' | 'every_15_minutes' | 'hourly'
+  sync_frequency TEXT NOT NULL DEFAULT 'hourly'
+    CHECK (sync_frequency IN ('realtime','every_15_minutes','hourly')),
+
+  sync_enabled BOOLEAN NOT NULL DEFAULT false,
+
+  -- Set after every sync attempt (success or failure).
+  last_sync_at TIMESTAMPTZ,
+  last_sync_error TEXT,
+
+  -- User IDs from `neon_auth.user`; stored as text so we don't
+  -- require a FK to a specific auth backend.
+  created_by TEXT,
+  updated_by TEXT,
+
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- Auto-bump updated_at on row UPDATE.
+DROP TRIGGER IF EXISTS water_smartsheet_config_set_updated_at ON water_smartsheet_config;
+CREATE TRIGGER water_smartsheet_config_set_updated_at
+  BEFORE UPDATE ON water_smartsheet_config
+  FOR EACH ROW EXECUTE FUNCTION set_updated_at();
+
+-- RLS: brand-scoped.
+ALTER TABLE water_smartsheet_config ENABLE ROW LEVEL SECURITY;
+
+DROP POLICY IF EXISTS tenant_isolation ON water_smartsheet_config;
+CREATE POLICY tenant_isolation ON water_smartsheet_config FOR ALL
+  USING (brand_id = current_brand_id() OR is_platform_admin())
+  WITH CHECK (brand_id = current_brand_id() OR is_platform_admin());
+
+-- ── 2. Sync queue (one row per water_log_entry awaiting sync) ──────────────
+
+CREATE TABLE IF NOT EXISTS water_smartsheet_sync_queue (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  brand_id UUID NOT NULL REFERENCES brands(id) ON DELETE CASCADE,
+
+  -- FK to the entry. ON DELETE CASCADE means deleting an entry also
+  -- removes its queue row, preventing orphaned sync attempts.
+  entry_id UUID NOT NULL REFERENCES water_log_entries(id) ON DELETE CASCADE,
+
+  -- The Smartsheet row ID returned from a successful sync.
+  -- NULL = not yet synced.
+  smartsheet_row_id TEXT,
+
+  -- 'pending' | 'syncing' | 'synced' | 'failed'
+  status TEXT NOT NULL DEFAULT 'pending'
+    CHECK (status IN ('pending','syncing','synced','failed')),
+
+  -- Bumped on every attempt (success or failure). Caps at 5 (after
+  -- which the row stays 'failed' permanently; admin must re-enable).
+  attempts INT NOT NULL DEFAULT 0,
+
+  -- Last failure reason (sanitized — token never appears here).
+  last_error TEXT,
+
+  -- When the next retry is allowed. Set to NOW() initially; pushed
+  -- out by exponential backoff on failure (2^attempts minutes, cap 1h).
+  next_attempt_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  synced_at TIMESTAMPTZ,
+
+  -- One queue row per entry per brand. CASCADE handles the case where
+  -- the entry is deleted (rare; only via admin override).
+  CONSTRAINT water_smartsheet_queue_entry_unique UNIQUE (brand_id, entry_id)
+);
+
+-- Hot path: drain query scans `(brand_id, status, next_attempt_at)`.
+CREATE INDEX IF NOT EXISTS water_smartsheet_queue_brand_status_idx
+  ON water_smartsheet_sync_queue (brand_id, status, next_attempt_at);
+
+-- Recent-attempts view.
+CREATE INDEX IF NOT EXISTS water_smartsheet_queue_brand_created_idx
+  ON water_smartsheet_sync_queue (brand_id, created_at DESC);
+
+ALTER TABLE water_smartsheet_sync_queue ENABLE ROW LEVEL SECURITY;
+
+DROP POLICY IF EXISTS tenant_isolation ON water_smartsheet_sync_queue;
+CREATE POLICY tenant_isolation ON water_smartsheet_sync_queue FOR ALL
+  USING (brand_id = current_brand_id() OR is_platform_admin())
+  WITH CHECK (brand_id = current_brand_id() OR is_platform_admin());
+
+-- ── 3. Sync log (append-only, backs Recent Activity UI) ────────────────────
+
+CREATE TABLE IF NOT EXISTS water_smartsheet_sync_log (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  brand_id UUID NOT NULL REFERENCES brands(id) ON DELETE CASCADE,
+
+  entry_id UUID REFERENCES water_log_entries(id) ON DELETE SET NULL,
+  smartsheet_row_id TEXT,
+
+  -- 'sync' (initial push) | 'retry' (after a failure) | 'skip'
+  -- (dedup hit — entry already had smartsheet_row_id) | 'test'
+  -- (the "Test Connection" button does NOT log here; that's a config
+  -- event recorded via water_audit_log instead).
+  action TEXT NOT NULL
+    CHECK (action IN ('sync','retry','skip','queue')),
+
+  success BOOLEAN NOT NULL,
+  error TEXT,
+  duration_ms INT,
+
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS water_smartsheet_log_brand_recent_idx
+  ON water_smartsheet_sync_log (brand_id, created_at DESC);
+
+ALTER TABLE water_smartsheet_sync_log ENABLE ROW LEVEL SECURITY;
+
+DROP POLICY IF EXISTS tenant_isolation ON water_smartsheet_sync_log;
+CREATE POLICY tenant_isolation ON water_smartsheet_sync_log FOR ALL
+  USING (brand_id = current_brand_id() OR is_platform_admin())
+  WITH CHECK (brand_id = current_brand_id() OR is_platform_admin());
+
+-- ── 4. Helper view: latest sync per entry (for dedup decisions) ────────────
+
+-- One row per entry with the most recent sync attempt. Used by the
+-- sync service to decide "has this entry been pushed already?".
+CREATE OR REPLACE VIEW water_smartsheet_latest_sync AS
+SELECT DISTINCT ON (q.brand_id, q.entry_id)
+  q.brand_id,
+  q.entry_id,
+  q.smartsheet_row_id,
+  q.status,
+  q.attempts,
+  q.last_error,
+  q.next_attempt_at,
+  q.created_at AS queued_at,
+  q.synced_at
+FROM water_smartsheet_sync_queue q
+ORDER BY q.brand_id, q.entry_id, q.created_at DESC;
+
+COMMENT ON TABLE water_smartsheet_config IS
+  'Per-brand Smartsheet integration config. Token is AES-256-GCM encrypted.';
+COMMENT ON TABLE water_smartsheet_sync_queue IS
+  'One row per water_log_entry awaiting / completed sync to Smartsheet.';
+COMMENT ON TABLE water_smartsheet_sync_log IS
+  'Append-only audit of Smartsheet sync attempts (success and failure).';