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

AGENTS.md

@@ -1,5 +1,15 @@
 # AGENTS.md
 
+## Important: File Path Convention
+
+**All file paths in this document and code references must use full absolute paths.**
+
+Examples:
+- ✅ `/Users/accusys/momentry_studio/src/views/PeopleView.vue`
+- ❌ `src/views/PeopleView.vue`
+- ✅ `/Users/accusys/momentry_studio/src-tauri/src/db.rs`
+- ❌ `src-tauri/src/db.rs`
+
 ## Stack
 - **Frontend**: Vue 3 + TypeScript + Vite (port 5173)
 - **Desktop**: Tauri 2 (Rust backend in `src-tauri/`)
@@ -7,13 +17,15 @@
 
 ## Commands
 ```
-npm run dev          # Vite dev server (port 5173)
+npm run proxy        # Start Rust proxy binary only (port 8888)
+npm run dev          # Start Rust proxy + Vite dev server (port 5173)
 npm run build        # vue-tsc --noEmit && vite build (typecheck + bundle)
 npm run preview      # Preview production build
 npm run tauri        # Alias for `cargo tauri`
 cargo tauri dev      # Full Tauri desktop dev (builds frontend + opens native window)
 cargo tauri build    # Full native app build (outputs to src-tauri/target/release/bundle/)
 ```
+- **Browser dev flow**: `npm run dev` → kills old proxy on 8888 → starts `momentry-proxy` → sleeps 2s → starts Vite. Vite proxy forwards `/api/v1/*` to Rust proxy at `localhost:8888`. Rust proxy handles face-crop, cluster-results, identity-matches, search-history, bookmarks, profile images locally; proxies rest to Core API at `localhost:3002`.
 
 ## Architecture
 - **Dual-mode API**: Frontend uses `apiCall()` from `src/api/index.ts` which detects `window.__TAURI__` and dispatches to either Tauri IPC (`invoke`) or HTTP to proxy at `http://0.0.0.0:8888`.