feat(water-log): add manual backfill to push historical entries to Smartsheet

Adds a backfill button to the Smartsheet Integration card so brand admins
can push existing water log entries (all time / last 30d / last 7d) to
their Smartsheet sheet — important for customers who configure
Smartsheet after months/years of recording entries.

- New enqueueSmartsheetBackfill(brandId, {since?}) server action:
  - Counts candidates, enqueues in 500-row chunks with
    onConflictDoNothing (UNIQUE on brand_id+entry_id absorbs dups).
  - Runs one inline drain pass (batchSize=200) for immediate feedback.
  - Cron picks up remaining queue rows across the next ticks.
  - Requires active Smartsheet config and admin permission; logs an
    audit event for the backfill.
- New "Backfill historical entries" card in SmartsheetIntegrationCard
  with range selector, confirmation prompt, and inline result feedback
  (counts of newly queued / already queued / drained synced / skipped /
  failed / remaining).
- Sync engine dedup by Entry ID + UNIQUE constraint means re-runs are
  safe: re-running never creates duplicate Smartsheet rows.

src/components/admin/water-log/SmartsheetIntegrationCard.tsx

@@ -32,6 +32,8 @@ import {
   saveSmartsheetConfig,
   testSmartsheetConnection,
   listSmartsheetSyncLog,
+  enqueueSmartsheetBackfill,
+  type EnqueueBackfillResult,
   type SmartsheetConfigResponse,
   type SmartsheetSyncLogEntry,
 } from "@/actions/water-log/smartsheet";
@@ -97,6 +99,12 @@ type State = {
   loadingLog: boolean;
   /** Whether the setup-instructions modal is open. */
   setupModalOpen: boolean;
+  /** Backfill UI state. */
+  backfill: {
+    running: boolean;
+    range: "all" | "30d" | "7d";
+    result: EnqueueBackfillResult | null;
+  };
 };
 
 type Action =
@@ -118,7 +126,10 @@ type Action =
   | { type: "CLEAR_MESSAGE" }
   | { type: "REFRESH_LOG"; log: SmartsheetSyncLogEntry[] }
   | { type: "OPEN_SETUP_MODAL" }
-  | { type: "CLOSE_SETUP_MODAL" };
+  | { type: "CLOSE_SETUP_MODAL" }
+  | { type: "BACKFILL_START" }
+  | { type: "BACKFILL_RANGE"; value: "all" | "30d" | "7d" }
+  | { type: "BACKFILL_DONE"; result: EnqueueBackfillResult };
 
 const EMPTY_MAPPING: SmartsheetColumnMapping = {
   entry_id: "",
@@ -146,6 +157,7 @@ const initialState: State = {
   recentLog: [],
   loadingLog: false,
   setupModalOpen: false,
+  backfill: { running: false, range: "all", result: null },
 };
 
 function reducer(state: State, action: Action): State {
@@ -227,6 +239,25 @@ function reducer(state: State, action: Action): State {
       return { ...state, setupModalOpen: true };
     case "CLOSE_SETUP_MODAL":
       return { ...state, setupModalOpen: false };
+    case "BACKFILL_START":
+      return {
+        ...state,
+        backfill: { ...state.backfill, running: true },
+      };
+    case "BACKFILL_RANGE":
+      return {
+        ...state,
+        backfill: { ...state.backfill, range: action.value },
+      };
+    case "BACKFILL_DONE":
+      return {
+        ...state,
+        backfill: {
+          ...state.backfill,
+          running: false,
+          result: action.result,
+        },
+      };
     default:
       return state;
   }
@@ -313,6 +344,50 @@ export default function SmartsheetIntegrationCard({
     }
   }
 
+  async function handleBackfill() {
+    if (state.backfill.running) return;
+    if (!state.savedConfig?.configured || !state.enabled) {
+      // Surface as a notice rather than call into the action just to fail.
+      dispatch({
+        type: "BACKFILL_DONE",
+        result: {
+          success: false,
+          error: "Save and enable your Smartsheet config first.",
+          considered: 0,
+          newlyQueued: 0,
+          alreadyQueued: 0,
+          drained: { synced: 0, skipped: 0, failed: 0, remaining: 0 },
+        },
+      });
+      return;
+    }
+    const rangeLabel =
+      state.backfill.range === "30d"
+        ? "the last 30 days"
+        : state.backfill.range === "7d"
+          ? "the last 7 days"
+          : "all time";
+    if (
+      !window.confirm(
+        `Sync ${rangeLabel} of water log entries to Smartsheet? This is safe to re-run — already-pushed entries are deduped by Entry ID.`,
+      )
+    ) {
+      return;
+    }
+    dispatch({ type: "BACKFILL_START" });
+    const since =
+      state.backfill.range === "30d"
+        ? new Date(Date.now() - 30 * 86_400_000)
+        : state.backfill.range === "7d"
+          ? new Date(Date.now() - 7 * 86_400_000)
+          : undefined;
+    const result = await enqueueSmartsheetBackfill(brandId, { since });
+    dispatch({ type: "BACKFILL_DONE", result });
+    // Refresh the log so the drain results show up immediately.
+    const log = await listSmartsheetSyncLog(brandId, 10);
+    dispatch({ type: "REFRESH_LOG", log });
+  }
+
   if (state.loading) {
     return (
       <Card title="Smartsheet Integration" subtitle="Loading…">
@@ -570,6 +645,8 @@ export default function SmartsheetIntegrationCard({
         </div>
       </Card>
 
+      <BackfillCard state={state.backfill} onRun={handleBackfill} onRangeChange={(v) => dispatch({ type: "BACKFILL_RANGE", value: v })} />
+
       <Card
         title="Recent activity"
         subtitle="Last 10 sync attempts. Use this to spot token / sheet issues quickly."
@@ -730,6 +807,123 @@ function TestResultPanel({ test }: { test: TestState }) {
   );
 }
 
+// ── Backfill card ──────────────────────────────────────────────────────────
+
+type BackfillState = {
+  running: boolean;
+  range: "all" | "30d" | "7d";
+  result: EnqueueBackfillResult | null;
+};
+
+function BackfillCard({
+  state,
+  onRun,
+  onRangeChange,
+}: {
+  state: BackfillState;
+  onRun: () => void;
+  onRangeChange: (value: "all" | "30d" | "7d") => void;
+}) {
+  const result = state.result;
+  // Success block — counts from the inline drain that ran after enqueue.
+  const showResult = result && result.success;
+  const showError = result && !result.success;
+
+  return (
+    <Card
+      title="Backfill historical entries"
+      subtitle="Push existing water log entries to your Smartsheet. Safe to re-run — already-pushed entries are deduped by Entry ID."
+    >
+      <div className="space-y-3">
+        <div className="flex flex-wrap items-center gap-3">
+          <label
+            htmlFor="smartsheet-backfill-range"
+            className="text-sm font-medium text-[#1d1d1f]"
+          >
+            Range
+          </label>
+          <select
+            id="smartsheet-backfill-range"
+            value={state.range}
+            onChange={(e) =>
+              onRangeChange(e.target.value as "all" | "30d" | "7d")
+            }
+            className="rounded-lg border border-[#d4d9d3] bg-white px-3 py-2 text-sm outline-none focus:border-[#1a4d2e] focus:ring-1 focus:ring-[#1a4d2e]"
+            disabled={state.running}
+          >
+            <option value="all">All time</option>
+            <option value="30d">Last 30 days</option>
+            <option value="7d">Last 7 days</option>
+          </select>
+          <button
+            type="button"
+            onClick={onRun}
+            disabled={state.running}
+            className="rounded-lg border border-[#1a4d2e] bg-white px-4 py-2 text-sm font-semibold text-[#1a4d2e] transition hover:bg-[#1a4d2e] hover:text-white disabled:opacity-50"
+          >
+            {state.running ? "Running backfill…" : "Run backfill"}
+          </button>
+        </div>
+
+        {state.running && (
+          <p className="text-xs text-[#5a5d5a]">
+            Counting entries, enqueueing, and draining one batch inline. Any
+            remaining entries will be drained by the cron (every 15 minutes).
+          </p>
+        )}
+
+        {showError && (
+          <div className="rounded-lg border border-[#a4452b] bg-[#a4452b]/5 px-3 py-2 text-xs">
+            <p className="font-semibold text-[#a4452b]">✗ {result.error}</p>
+          </div>
+        )}
+
+        {showResult && result && (
+          <div className="rounded-lg border border-[#1a4d2e] bg-[#1a4d2e]/5 px-3 py-2 text-xs">
+            <p className="font-semibold text-[#1a4d2e]">
+              ✓ Found {result.considered}{" "}
+              {result.considered === 1 ? "entry" : "entries"} matching the
+              range
+              {result.considered > 0 && (
+                <>
+                  {" "}
+                  ({result.newlyQueued} new, {result.alreadyQueued} already
+                  queued).
+                </>
+              )}
+              .
+            </p>
+            {(result.drained.synced +
+              result.drained.skipped +
+              result.drained.failed >
+              0 || result.drained.remaining > 0) && (
+              <p className="mt-1 text-[#1d1d1f]">
+                Inline drain: {result.drained.synced} synced /{" "}
+                {result.drained.skipped} skipped / {result.drained.failed}{" "}
+                failed.
+                {result.drained.remaining > 0 && (
+                  <>
+                    {" "}
+                    <strong className="text-[#1a4d2e]">
+                      {result.drained.remaining} still queued
+                    </strong>{" "}
+                    — they&apos;ll drain on the next cron tick (within 15
+                    minutes).
+                  </>
+                )}
+                {result.drained.remaining === 0 &&
+                  result.considered > 0 && (
+                    <> All entries are now in Smartsheet.</>
+                  )}
+              </p>
+            )}
+          </div>
+        )}
+      </div>
+    </Card>
+  );
+}
+
 // ── Setup instructions modal ───────────────────────────────────────────────
 
 const FIELD_SCHEMA: Array<{