fix: gemini route, usage capture, search timeout, and trace finalization

- Add missing /v1/gemini POST route and handler
- Capture MitmEvent::Usage in gemini sync/streaming handlers
- Add retry counter (max 3) to search handler to prevent hang
- Add trace finalization at all gemini_sync channel exit points
- Fix UpstreamError trace outcome label
- Add timeout trace with error recording
- Dispatch Usage before ResponseComplete in SSE flush

src/api/mod.rs

@@ -33,6 +33,10 @@ pub struct AppState {
     pub sessions: SessionManager,
     pub mitm_store: crate::mitm::store::MitmStore,
     pub quota_store: crate::quota::QuotaStore,
+    /// Whether the MITM proxy is active (false when --no-mitm).
+    pub mitm_enabled: bool,
+    /// Per-call debug trace collector.
+    pub trace: crate::trace::TraceCollector,
 }
 
 // ─── Router ──────────────────────────────────────────────────────────────────
@@ -44,6 +48,7 @@ pub fn router(state: Arc<AppState>) -> Router {
             "/v1/chat/completions",
             post(completions::handle_completions),
         )
+        .route("/v1/gemini", post(gemini::handle_gemini))
         .route(
             "/v1beta/{*path}",
             post(gemini::handle_gemini_v1beta),