feat(arayüz): API istemcisi, TanStack Query, ts-rs tip üretimi ve oturum durumu

- Backend: ts-rs ile DTO'lardan TypeScript tipleri (frontend/src/types, npm run types)
- Hata ve health yanıtları tipli yapılara çevrildi
- lib/api.ts: tek API istemcisi, Türkçe ApiError, ağ hatası mesajı
- lib/query.ts: QueryClient (4xx tekrar denenmez, 401 → oturum kapanır)
- lib/auth.ts: useMe, useLogin, useRegister, useLogout
- Vitest: 7 API istemcisi testi (toplam 29)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/src/routes/health.rs

@@ -1,23 +1,42 @@
 use axum::{Json, extract::State, http::StatusCode};
-use serde_json::{Value, json};
+use serde::Serialize;
+use ts_rs::TS;
 
 use crate::{db, state::AppState};
 
+#[derive(Serialize, TS)]
+#[ts(export)]
+pub struct HealthResponse {
+    /// `ok` veya `degraded`
+    status: &'static str,
+    /// `ok` veya `error`
+    db: &'static str,
+    version: &'static str,
+}
+
 /// Sağlık kontrolü (Dokploy health check bunu kullanır).
 /// DB erişilemezse 503 döner.
-pub async fn health(State(state): State<AppState>) -> (StatusCode, Json<Value>) {
+pub async fn health(State(state): State<AppState>) -> (StatusCode, Json<HealthResponse>) {
     let version = env!("CARGO_PKG_VERSION");
 
     match db::ping(&state.db).await {
         Ok(()) => (
             StatusCode::OK,
-            Json(json!({ "status": "ok", "db": "ok", "version": version })),
+            Json(HealthResponse {
+                status: "ok",
+                db: "ok",
+                version,
+            }),
         ),
         Err(e) => {
             tracing::warn!(error = %e, "health: veritabanına erişilemiyor");
             (
                 StatusCode::SERVICE_UNAVAILABLE,
-                Json(json!({ "status": "degraded", "db": "error", "version": version })),
+                Json(HealthResponse {
+                    status: "degraded",
+                    db: "error",
+                    version,
+                }),
             )
         }
     }