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/seo.ts

@@ -0,0 +1,53 @@
+import "server-only";
+import type { Metadata } from "next";
+import { getSeoPage, getSeoSettings } from "@/lib/data";
+import { siteConfig } from "@/lib/site-config";
+
+export async function buildMetadata(path: string, fallback?: Metadata): Promise<Metadata> {
+  const [settings, override] = await Promise.all([
+    getSeoSettings(),
+    getSeoPage(path),
+  ]);
+
+  const siteName = settings?.site_name || siteConfig.name;
+  const siteDesc = settings?.site_description || siteConfig.tagline;
+  const ogDefault = settings?.default_og_image || "/logo.png";
+
+  const title =
+    override?.title ?? (fallback?.title as string | undefined) ?? siteName;
+  const description =
+    override?.description ??
+    (fallback?.description as string | undefined) ??
+    siteDesc;
+  const ogImage = override?.og_image || ogDefault;
+
+  return {
+    title,
+    description,
+    metadataBase: new URL(siteConfig.url),
+    openGraph: {
+      title,
+      description,
+      images: ogImage ? [{ url: ogImage }] : undefined,
+      type: "website",
+      locale: "tr_TR",
+      siteName,
+    },
+    twitter: {
+      card: "summary_large_image",
+      title,
+      description,
+      images: ogImage ? [ogImage] : undefined,
+      site: settings?.twitter_handle ?? undefined,
+    },
+    alternates: override?.canonical
+      ? { canonical: override.canonical }
+      : undefined,
+    robots: override?.noindex
+      ? { index: false, follow: false }
+      : undefined,
+    verification: settings?.google_site_verification
+      ? { google: settings.google_site_verification }
+      : undefined,
+  };
+}