fix(WP-0014): pre-flight compilation fixes, Tailwind pipeline, and admin seed

A2 — Compilation fixes:
- Remove inline FK constraints from Schema.sql; IHP schema compiler cannot
  parse them. Add 1744329600-restore-fk-constraints.sql migration to restore
  referential integrity at the DB level.
- Rename `#label` → `#label_` throughout to avoid clash with Haskell built-in.
- Fix `hub.id == hid` UUID comparisons to use `toUUID hub.id`.
- Replace non-existent `setStatus`/`respondJson` calls with
  `renderJsonWithStatusCode` throughout Api controllers.
- Fix qualified package import for `cryptohash-sha256` in Auth.hs.
- Add `CanSelect (Text, Text)` instance in Helper.View.
- Refactor HSX inline lambdas to named helper functions in 100+ views
  (GHC cannot infer types for anonymous functions inside quasi-quoted HSX).
- Fix missing imports (IHP.QueryBuilder, IHP.Fetch, Web.Routes, Only, etc.)
  across helpers and controllers.
- Remove duplicate `diffUTCTime` definition in BottleneckDetector.
- Change `createEventForHub` return type from `IO ResponseReceived` to `IO ()`.
- Seed type-registry vocabulary via 1744502400-seed-type-registries.sql
  (moved from Schema.sql where IHP does not execute INSERT statements).

A3 — Tailwind build pipeline:
- Add `tailwindcss` to flake.nix native packages.
- Uncomment `tailwind.exec` process in devenv shell config.
- Add tailwind/tailwind.config.js (scans Web/View/**/*.hs).
- Add tailwind/app.css with @tailwind directives.

A4 — Admin user seed:
- Add 1744416000-seed-admin-user.sql: inserts admin@inter-hub.local
  with bcrypt-hashed password admin1234! (cost 10).
- Add .env.example documenting all required environment variables
  and default admin credentials.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Application/Migration/1744416000-seed-admin-user.sql

@@ -0,0 +1,15 @@
+-- Seed default admin user for initial local deployment.
+-- Password: admin1234!
+-- Hash generated with bcrypt cost 10 (compatible with IHP's authenticate @User).
+-- IMPORTANT: Change this password immediately after first login via the profile settings.
+-- Workplan: IHUB-WP-0014 (A4 — admin user seeding)
+
+INSERT INTO users (id, email, password_hash, name, failed_login_attempts, created_at)
+VALUES (
+    uuid_generate_v4(),
+    'admin@inter-hub.local',
+    '$2b$10$c3imjL8nLkR1TSbBifvR3eFzlCUurGPXsN7K5trDjmZL6Af3zLqH.',
+    'Admin',
+    0,
+    now()
+);