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)/medya/page.tsx

@@ -1,7 +1,6 @@
 import { PageHeader } from "@/components/admin/form";
-import { MEDIA_BUCKET_ID, userStorage } from "@/lib/appwrite-server";
+import { MEDIA_BUCKET_ID, Q, storage } from "@/lib/appwrite-rest";
 import { requireSessionSecret } from "@/lib/auth";
-import { Query } from "appwrite";
 import { Upload } from "lucide-react";
 import { DeleteButton } from "@/components/admin/delete-button";
 import { uploadMedia, deleteMediaFile } from "@/lib/admin-actions";
@@ -9,10 +8,11 @@ import { uploadMedia, deleteMediaFile } from "@/lib/admin-actions";
 async function listFiles() {
   try {
     const secret = await requireSessionSecret();
-    const res = await userStorage(secret).listFiles({
-      bucketId: MEDIA_BUCKET_ID,
-      queries: [Query.orderDesc("$createdAt"), Query.limit(100)],
-    });
+    const res = await storage.listFiles(
+      MEDIA_BUCKET_ID,
+      [Q.orderDesc("$createdAt"), Q.limit(100)],
+      secret,
+    );
     return res.files;
   } catch {
     return [];
@@ -20,7 +20,7 @@ async function listFiles() {
 }
 
 function fileViewUrl(id: string) {
-  return `${process.env.NEXT_PUBLIC_APPWRITE_ENDPOINT}/storage/buckets/${MEDIA_BUCKET_ID}/files/${id}/view?project=${process.env.NEXT_PUBLIC_APPWRITE_PROJECT_ID}`;
+  return storage.fileViewUrl(MEDIA_BUCKET_ID, id);
 }
 
 export default async function MediaPage() {