feat: frame-based positioning and mark system foundation

Core Changes:
- Fix SearchView to use start_frame/end_frame directly (no time*fps conversion)
- Add hard_delete support to delete_trace API
- VideoPlayer: Main timeline + Mark system foundation
- Proxy: Add local routes for auth, media, identity-matches, cluster-results
- Add .gitignore to exclude build artifacts and dependencies

Design Documents:
- Multi-track Mark system design (.opencode/plans/)
- Video editing positioning standards research

Files Modified:
- src/views/SearchView.vue: Frame positioning, ensureMinDuration (240 frames)
- src/views/PeopleView.vue: batchDeleteGroups with hard_delete
- src/api/index.ts: delete_trace with hard_delete body
- src/components/VideoPlayer.vue: Timeline + Mark UI
- src-tauri/src/proxy.rs: New local routes
- AGENTS.md: Update documentation

src-tauri/src/bin/proxy.rs

@@ -1,11 +1,11 @@
-// Standalone proxy binary for testing/development
-// Re-exports the proxy module from main crate
+#[path = "../proxy.rs"]
+mod proxy;
 
-fn main() {
-    // We can't import from the main crate as a library easily,
-    // so instead we'll just call through the Tauri binary mechanism.
-    // For now, the full Tauri binary must be used to run the proxy.
-    eprintln!("Use `cargo tauri dev` to start the full application with proxy.");
-    eprintln!("For standalone proxy testing, the proxy runs as part of the Tauri binary.");
-    std::process::exit(1);
+#[path = "../db.rs"]
+mod db;
+
+#[tokio::main]
+async fn main() {
+    let _ = db::init_db();
+    proxy::start_proxy_server().await;
 }