fix: auth login flow, Next.js 16 upgrade, ESM/CJS compatibility

- Upgrade Next.js 15 → 16.1 and rename middleware.ts → proxy.ts
- Fix ESM/CJS compatibility: remove "type": "module" from config/shared packages, switch to commonjs
- Fix Better Auth integration: text IDs for sessions/accounts/verifications, wildcard route @All("**"), proper password hash for admin seed
- Fix auth-client to use window.location.origin instead of hardcoded localhost:4000
- Fix api-client, forgot-password, reset-password to use relative /api/ URLs (via Next.js proxy)
- Fix TimeoutInterceptor DI by using useValue instead of useClass
- Add Playwright E2E login tests for localhost and v2.sase.tr
- Add missing UI components: vin-input, vehicle-card, category-tree

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

packages/shared/tsconfig.json

@@ -1,8 +1,8 @@
 {
   "compilerOptions": {
     "target": "ES2022",
-    "module": "Node16",
-    "moduleResolution": "Node16",
+    "module": "commonjs",
+    "moduleResolution": "node",
     "lib": ["ES2022"],
     "strict": true,
     "esModuleInterop": true,