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>

lib/auth/password.ts

@@ -0,0 +1,11 @@
+import bcryptjs from 'bcryptjs'
+
+const BCRYPT_ROUNDS = 10  // matches Supabase GoTrue default
+
+export async function hashPassword(plaintext: string): Promise<string> {
+  return bcryptjs.hash(plaintext, BCRYPT_ROUNDS)
+}
+
+export async function verifyPassword(plaintext: string, hash: string): Promise<boolean> {
+  return bcryptjs.compare(plaintext, hash)
+}