fix(auth): SDK'yı kaldırıp ince REST katmanına geç (lib/appwrite-rest.ts)

Sorun:
- node-appwrite v20-25 hepsi Node 26'da bozuk (node-fetch-native-with-agent polyfill)
- appwrite browser SDK Server Action context'inde 'unexpected response' veriyor
  (büyük olasılıkla browser-only global'ları kontrol ederken)

Çözüm:
- Tüm Appwrite SDK'larını sil (appwrite + node-appwrite)
- lib/appwrite-rest.ts: native fetch üzerinde ~250 satırlık ince REST wrapper
  - account: createEmailPasswordSession, get, deleteSession
  - tablesDB: listRows, getRow, createRow, updateRow, deleteRow
  - storage: listFiles, createFile, deleteFile, fileViewUrl
  - Q helpers: equal, orderAsc/Desc, limit, offset
  - AppwriteError class
- Session secret cookie tabanlı auth korundu (isletmem-kovakcrm'deki desen)
- Tüm CRUD action ve query'ler REST katmanına bağlandı

End-to-end test edildi:
✓ Login (proper 401 hata mesajları, başarılı durumda redirect)
✓ Public read (services, blog, testimonials)
✓ Anonim create (contact form)
✓ Build (24 route)
✓ Sıfır SDK bağımlılığı — Node 26 sorunu yok

app/admin/(protected)/page.tsx

@@ -1,17 +1,17 @@
 import Link from "next/link";
 import { ArrowRight } from "lucide-react";
-import { Query } from "appwrite";
-import { DATABASE_ID, TABLES, userDB } from "@/lib/appwrite-server";
+import { DATABASE_ID, Q, TABLES, tablesDB } from "@/lib/appwrite-rest";
 import { requireSessionSecret } from "@/lib/auth";
 
 async function safeCount(tableId: string, queries: string[] = []) {
   try {
     const secret = await requireSessionSecret();
-    const res = await userDB(secret).listRows({
-      databaseId: DATABASE_ID,
+    const res = await tablesDB.listRows(
+      DATABASE_ID,
       tableId,
-      queries: [...queries, Query.limit(1)],
-    });
+      [...queries, Q.limit(1)],
+      secret,
+    );
     return res.total ?? 0;
   } catch {
     return 0;
@@ -21,12 +21,12 @@ async function safeCount(tableId: string, queries: string[] = []) {
 export default async function AdminDashboard() {
   const [posts, drafts, services, projects, testimonials, newMessages, totalMessages] =
     await Promise.all([
-      safeCount(TABLES.blogPosts, [Query.equal("status", "published")]),
-      safeCount(TABLES.blogPosts, [Query.equal("status", "draft")]),
+      safeCount(TABLES.blogPosts, [Q.equal("status", "published")]),
+      safeCount(TABLES.blogPosts, [Q.equal("status", "draft")]),
       safeCount(TABLES.services),
       safeCount(TABLES.projects),
       safeCount(TABLES.testimonials),
-      safeCount(TABLES.contactMessages, [Query.equal("status", "new")]),
+      safeCount(TABLES.contactMessages, [Q.equal("status", "new")]),
       safeCount(TABLES.contactMessages),
     ]);