ci(gitea): add deploy workflow + self-hosted homelab deploy toolkit (Auth.js port)

Ports the deploy pipeline from the Gitea main fork (commit 7ddb06d's deploy
toolkit) into the Auth.js v5 / NextAuth tree:

- .gitea/workflows/deploy.yml: inline deploy that brings up the Docker
  stack, applies migrations, builds Next.js, and runs the app under PM2.
  Swapped Better Auth env vars (BETTER_AUTH_SECRET/URL, NEXT_PUBLIC_BETTER_AUTH_URL)
  for Auth.js v5 names (AUTH_SECRET/URL, NEXT_PUBLIC_AUTH_URL). Dropped
  NEXT_PUBLIC_SUPABASE_URL/ANON_KEY (Supabase removal in progress). Added
  GOOGLE_CLIENT_ID/SECRET + ALLOW_DEV_LOGIN for the Auth.js Google provider
  and dev credentials path. Switched runs-on from 'ubuntu-latest' to the
  self-hosted runner labels matching build.yml.

- deploy/: idempotent deploy toolkit (deploy.sh, docker-compose.yml,
  Dockerfile.nextjs, nginx.conf.template, .env.production.example, healthcheck.sh,
  Makefile, deploy/.gitignore). No auth/Supabase dependencies — pure infra.

- deploy/.env.production.example: renamed NEXTAUTH_SECRET/NEXTAUTH_URL
  (v4) to AUTH_SECRET/AUTH_URL (v5) and added the v5-specific vars
  (NEXT_PUBLIC_AUTH_URL, GOOGLE_*, ALLOW_DEV_LOGIN).

Build pipeline is now end-to-end:
  build.yml → typecheck + lint + build (uses [self-hosted, linux, ubuntu-latest])
  deploy.yml → start docker stack + migrations + build + PM2 restart

Storage / admin code ports (MinIO via @/lib/storage, Supabase removal,
admin-permissions rewrite) are tracked separately — they require porting
the storage and admin code first; the deploy pipeline itself is ready
to run against the Auth.js world.

deploy/docker-compose.yml

@@ -0,0 +1,70 @@
+# =============================================================================
+# docker-compose.yml — production stack consumed by deploy.sh
+# =============================================================================
+#
+# The host-side ports (POSTGREST_HOST_PORT, NEXTJS_HOST_PORT) are written by
+# deploy.sh into .env.production. We interpolate from there with ${VAR:-3011}
+# so a manual `docker compose up` without the deploy script still works.
+#
+# Note on networking: the Next.js container calls PostgREST on
+# `host.docker.internal:POSTGREST_HOST_PORT` so the inlined
+# NEXT_PUBLIC_API_URL (a localhost URL, per the deploy contract) resolves
+# correctly. On Linux you may need to add
+#   extra_hosts:
+#     - "host.docker.internal:host-gateway"
+# which is included below for that reason.
+# =============================================================================
+
+name: prod-app  # default project name; deploy.sh overrides with -p
+
+services:
+  postgrest:
+    image: postgrest/postgrest:latest
+    container_name: prod-app-postgrest
+    restart: unless-stopped
+    # The host port is dynamic. The container always listens on 3000.
+    ports:
+      - "${POSTGREST_HOST_PORT:-3011}:3000"
+    environment:
+      PGRST_DB_URI: ${PGRST_DB_URI}
+      PGRST_DB_ANON_ROLE: ${PGRST_DB_ANON_ROLE:-anon}
+      PGRST_DB_SCHEMA: ${PGRST_DB_SCHEMA:-public}
+      PGRST_SERVER_PORT: 3000
+      # Optional: tighten CORS for your real domain
+      PGRST_DB_TXN_END: "commit-allow-overwrite"
+    # Healthcheck lets `docker compose ps` show healthy state.
+    healthcheck:
+      test: ["CMD", "wget", "-qO-", "http://127.0.0.1:3000/"]
+      interval: 10s
+      timeout: 3s
+      retries: 6
+
+  nextjs:
+    # Build context is the workspace root (one level up from this file).
+    build:
+      context: ..
+      dockerfile: deploy/Dockerfile.nextjs
+    container_name: prod-app-nextjs
+    restart: unless-stopped
+    ports:
+      - "${NEXTJS_HOST_PORT:-3012}:3000"
+    environment:
+      # Runtime vars — these can change without rebuilding. NEXT_PUBLIC_*
+      # is also exported here for completeness, but the BROWSER's view of
+      # NEXT_PUBLIC_API_URL is baked in at build time (see Dockerfile).
+      NODE_ENV: production
+      PORT: 3000
+      NEXT_PUBLIC_API_URL: ${NEXT_PUBLIC_API_URL}
+    env_file:
+      - ../.env.production   # server-side secrets read at runtime
+    extra_hosts:
+      # Lets the container reach the host on the dynamically allocated port.
+      - "host.docker.internal:host-gateway"
+    depends_on:
+      postgrest:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD", "wget", "-qO-", "http://127.0.0.1:3000/api/health"]
+      interval: 10s
+      timeout: 3s
+      retries: 6