Task #526: Off-Replit migration & GitHub-ready cleanup

Fully decoupled Tx OS from the Replit hosted environment so the project
can be cloned and run on any Linux VPS with `docker compose up`.

Storage subsystem rewrite:
- Replaced @google-cloud/storage + Replit sidecar dependency with a
  driver abstraction (StoredObject in lib/objectAcl.ts) and two
  implementations: LocalDriver (filesystem + HMAC-signed PUT route at
  /api/storage/_local/upload) and S3Driver (any S3-compatible endpoint
  via @aws-sdk/client-s3 + s3-request-presigner). Driver auto-selected
  by STORAGE_DRIVER / S3_ENDPOINT env vars.
- Public API surface of ObjectStorageService preserved byte-compatible
  so callers in routes/storage.ts and routes/executive-meetings.ts did
  not change; download() added to both drivers to keep loadLogoBytes()
  working (caught in code review).
- Storage object-authz tests A-L (incl. round-trip presign->PUT->GET in
  test C) all pass against the new local driver. Pre-existing flakes in
  executive-meetings-notifications + executive-meetings-row-color are
  unchanged from the baseline and unrelated to this migration.

Infrastructure:
- Dockerfile (5 targets: deps/build/api/web/migrate). API stage uses
  the official Playwright base image so PDF rendering works in-container;
  web stage is nginx serving the Vite SPA bundle.
- docker-compose.yml: postgres + minio + minio-init (creates buckets) +
  api + web + one-shot migrate runner. Healthchecks on every long-lived
  service.
- docker/nginx.conf: SPA fallback, /api proxy, /api/socket.io websocket
  upgrade ordering.
- .env.example: every runtime env var documented with comments.
- README.md replaces replit.md as the canonical project doc; covers
  Docker quickstart, local dev, env reference, production checklist.
- MIGRATION_REPORT.md: file-by-file diff of what changed and why.

Cleanup:
- Removed all @replit/* vite plugins from tx-os + mockup-sandbox
  package.json + vite.config.ts + pnpm-workspace.yaml catalog.
- Removed @google-cloud/storage and google-auth-library from api-server.
- Deleted attached_assets/ (23MB), sedMkjeJm temp file, stale dist/ and
  *.tsbuildinfo build artefacts, scripts/post-merge.sh.
- Stripped Replit references from threat_model.md (now describes the
  self-hosted topology).
- New comprehensive .gitignore: Replit configs (.replit, replit.nix,
  replit.md), agent state (.local/, .canvas/, .agents/, .cache/, .config/,
  .upm/), local storage/, .env*, build artefacts. .replit and replit.nix
  remain on disk (sandbox-protected) but will not ship to GitHub.
- scripts/src/seed.ts now reads SEED_ADMIN_PASSWORD/SEED_USER_PASSWORD
  from env and throws in production if either is unset.

Drift from plan: replit.md was deleted (per off-Replit scope) so its
"do-not-touch files" preference list is moot. .replit/replit.nix kept on
disk only because they are sandbox-protected from edit/delete in this
environment, but they are git-ignored so they will not appear in a
fresh clone.

artifacts/api-server/package.json

@@ -12,7 +12,8 @@
     "test": "node --test 'tests/**/*.test.mjs'"
   },
   "dependencies": {
-    "@google-cloud/storage": "^7.19.0",
+    "@aws-sdk/client-s3": "^3.658.0",
+    "@aws-sdk/s3-request-presigner": "^3.658.0",
     "@swc/helpers": "^0.5.21",
     "@workspace/api-zod": "workspace:*",
     "@workspace/db": "workspace:*",
@@ -26,7 +27,6 @@
     "express": "^5",
     "express-rate-limit": "^8.5.1",
     "express-session": "^1.19.0",
-    "google-auth-library": "^10.6.2",
     "nodemailer": "^8.0.7",
     "pdfkit": "^0.18.0",
     "pino": "^9",