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

package-lock.json

@@ -8,7 +8,6 @@
       "name": "kovak-yazilim",
       "version": "0.1.0",
       "dependencies": {
-        "appwrite": "^25.1.1",
         "lucide-react": "^1.16.0",
         "marked": "^18.0.4",
         "next": "16.2.6",
@@ -1079,18 +1078,6 @@
         "@types/react": "^19.2.0"
       }
     },
-    "node_modules/appwrite": {
-      "version": "25.1.1",
-      "resolved": "https://registry.npmjs.org/appwrite/-/appwrite-25.1.1.tgz",
-      "integrity": "sha512-h+vVPErfCLZ9FCnWH1cZOphgX8MsXNNN0PvxCxoOCbqyX6XubtvvOEpp/BpVOAHp7jIDFEJu72ingBu9kh1vDQ==",
-      "license": "BSD-3-Clause",
-      "dependencies": {
-        "json-bigint": "1.0.0"
-      },
-      "engines": {
-        "node": ">=18.0.0"
-      }
-    },
     "node_modules/baseline-browser-mapping": {
       "version": "2.10.31",
       "resolved": "https://registry.npmjs.org/baseline-browser-mapping/-/baseline-browser-mapping-2.10.31.tgz",
@@ -1103,15 +1090,6 @@
         "node": ">=6.0.0"
       }
     },
-    "node_modules/bignumber.js": {
-      "version": "9.3.1",
-      "resolved": "https://registry.npmjs.org/bignumber.js/-/bignumber.js-9.3.1.tgz",
-      "integrity": "sha512-Ko0uX15oIUS7wJ3Rb30Fs6SkVbLmPBAKdlm7q9+ak9bbIeFf0MwuBsQV6z7+X768/cHsfg+WlysDWJcmthjsjQ==",
-      "license": "MIT",
-      "engines": {
-        "node": "*"
-      }
-    },
     "node_modules/caniuse-lite": {
       "version": "1.0.30001793",
       "resolved": "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001793.tgz",
@@ -1186,15 +1164,6 @@
         "jiti": "lib/jiti-cli.mjs"
       }
     },
-    "node_modules/json-bigint": {
-      "version": "1.0.0",
-      "resolved": "https://registry.npmjs.org/json-bigint/-/json-bigint-1.0.0.tgz",
-      "integrity": "sha512-SiPv/8VpZuWbvLSMtTDU8hEfrZWg/mH/nV/b4o0CYbSxu1UIQPLdwKOCIyLQX+VIPO5vrLX3i8qtqFyhdPSUSQ==",
-      "license": "MIT",
-      "dependencies": {
-        "bignumber.js": "^9.0.0"
-      }
-    },
     "node_modules/lightningcss": {
       "version": "1.32.0",
       "resolved": "https://registry.npmjs.org/lightningcss/-/lightningcss-1.32.0.tgz",