feat: admin paneli + blog + testimonials + SEO yöneticisi

Backend altyapısı:
- 4 yeni Appwrite tablosu: blog_posts, testimonials, seo_pages, seo_settings
- Appwrite Storage bucket: kovak-yazilim-media (görsel yüklemeleri)
- Appwrite Auth ile session cookie tabanlı koruma

Admin paneli (/admin):
- Login akışı (email/password) + protected layout
- Dashboard: sayım kartları + hızlı aksiyonlar
- Blog CRUD: markdown content, kapak görseli, draft/published, SEO alanları
- Services CRUD: lucide ikon seçici
- Projects CRUD: teknoloji etiketleri, live URL
- Testimonials CRUD: puanlama
- SEO yöneticisi: global ayarlar + sayfa bazlı override
- Mesaj inbox: status filtreleme + güncelleme
- Medya kütüphanesi: Appwrite Storage upload/delete

Public:
- /blog ve /blog/[slug] sayfaları (markdown render)
- Anasayfaya Testimonials bölümü
- Tüm public sayfalarda generateMetadata + seo_pages override
- Header'a Blog linki

Route yapısı:
- app/(site)/ — public site, Header/Footer ortak
- app/admin/login — auth dışı
- app/admin/(protected)/ — requireUser() korumalı

23 route üretiliyor, public static, admin dynamic.

lib/appwrite-server.ts

@@ -1,23 +1,39 @@
 import "server-only";
-import { Client, TablesDB } from "node-appwrite";
+import { Account, Client, Storage, TablesDB } from "node-appwrite";
 
 const endpoint = process.env.NEXT_PUBLIC_APPWRITE_ENDPOINT!;
 const projectId = process.env.NEXT_PUBLIC_APPWRITE_PROJECT_ID!;
 const apiKey = process.env.APPWRITE_API_KEY;
 
 export const DATABASE_ID = process.env.NEXT_PUBLIC_APPWRITE_DATABASE_ID!;
+export const MEDIA_BUCKET_ID =
+  process.env.NEXT_PUBLIC_APPWRITE_MEDIA_BUCKET_ID ?? "kovak-yazilim-media";
 
 export const TABLES = {
   contactMessages: "contact_messages",
   services: "services",
   projects: "projects",
+  blogPosts: "blog_posts",
+  testimonials: "testimonials",
+  seoPages: "seo_pages",
+  seoSettings: "seo_settings",
 } as const;
 
-function buildClient() {
+export function adminClient() {
   const c = new Client().setEndpoint(endpoint).setProject(projectId);
   if (apiKey) c.setKey(apiKey);
   return c;
 }
 
-export const serverClient = buildClient();
-export const serverTablesDB = new TablesDB(serverClient);
+export function sessionClient(sessionSecret: string) {
+  return new Client()
+    .setEndpoint(endpoint)
+    .setProject(projectId)
+    .setSession(sessionSecret);
+}
+
+export const adminDB = new TablesDB(adminClient());
+export const adminStorage = new Storage(adminClient());
+export const adminAccount = new Account(adminClient());
+
+export { Account, TablesDB, Storage };