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/Cargo.toml

@@ -30,11 +30,14 @@ base64 = "0.22"
 lru = "0.12"
 futures = "0.3"
 image = { version = "0.24", default-features = false, features = ["jpeg"] }
+kamadak-exif = "0.6"
 axum = "0.7"
 tower-http = { version = "0.5", features = ["cors", "fs"] }
 rusqlite = { version = "0.32", features = ["bundled"] }
 chrono = { version = "0.4", features = ["serde"] }
 uuid = { version = "1", features = ["v4"] }
+argon2 = "0.5"
+rand = "0.8"
 # MarkBase Core for Admin/Client GUI
 markbase-core = { path = "../../markbase/markbase-core" }