feat(auth): phase 3 — replace Supabase GoTrue with bcryptjs+jose

Custom auth stack: bcryptjs password hashing (cost 10, GoTrue-compatible),
jose JWT session cookies (edge-safe, 8hr TTL), new API routes for
login/logout/reset/change-password, middleware rewritten to JWT-only
verification with no DB access. All 38 protected pages and API routes
migrated from supabase.auth.getUser() to getSession(). Supabase .from()
queries retained for Phase 4. lib/db/index.ts refactored to lazy Proxy
singleton to avoid module-level throw during Next.js build.

tsc: clean, build: clean, tests: 4/4 passed

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

supabase/migrations/20260724000001_password_reset_tokens.sql

@@ -0,0 +1,14 @@
+CREATE TABLE password_reset_tokens (
+  id         UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  user_id    UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  token_hash TEXT NOT NULL UNIQUE,
+  expires_at TIMESTAMPTZ NOT NULL,
+  used_at    TIMESTAMPTZ,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX password_reset_tokens_user_idx ON password_reset_tokens(user_id);
+CREATE INDEX password_reset_tokens_hash_idx ON password_reset_tokens(token_hash);
+
+-- password_reset_tokens: accessed via app_admin only (BYPASSRLS); no user-facing policies needed
+-- GRANT already covered by: GRANT ALL ON ALL TABLES IN SCHEMA public TO app_admin