refactor: modularize server.rs into separate route modules

- Extract scan.rs, files.rs, types.rs, processing.rs, visual_chunk_search.rs
- Move AppState and AppConfig to types.rs
- Each module exposes pub fn xxx_routes() -> Router<AppState>
- server.rs reduced from 5005 to 118 lines (orchestrator only)
- All stubs filled with real implementations from git history
- Verify: cargo check, clippy, tests all pass

src/api/universal_search.rs

@@ -98,7 +98,7 @@ pub enum SearchResult {
     },
 }
 
-pub fn universal_search_routes() -> Router<crate::api::server::AppState> {
+pub fn universal_search_routes() -> Router<crate::api::types::AppState> {
     Router::new()
         .route("/api/v1/search/universal", post(universal_search))
         .route("/api/v1/search/frames", post(search_frames))
@@ -106,7 +106,7 @@ pub fn universal_search_routes() -> Router<crate::api::server::AppState> {
 
 /// Unified search across all data types
 pub async fn universal_search(
-    State(_state): State<crate::api::server::AppState>,
+    State(_state): State<crate::api::types::AppState>,
     Json(req): Json<UniversalSearchRequest>,
 ) -> Result<Json<UniversalSearchResponse>, (StatusCode, Json<serde_json::Value>)> {
     let start_time = std::time::Instant::now();
@@ -212,7 +212,7 @@ pub async fn universal_search(
 
 /// Search frames by YOLO objects, OCR text, or face IDs
 pub async fn search_frames(
-    State(_state): State<crate::api::server::AppState>,
+    State(_state): State<crate::api::types::AppState>,
     Json(req): Json<FrameSearchRequest>,
 ) -> Result<Json<FrameSearchResponse>, (StatusCode, Json<serde_json::Value>)> {
     let db = PostgresDb::init().await.map_err(|e| {
@@ -238,7 +238,7 @@ pub async fn search_frames(
 
 /// Search persons by name or speaker_id
 pub async fn search_persons(
-    State(_state): State<crate::api::server::AppState>,
+    State(_state): State<crate::api::types::AppState>,
     Query(query): Query<PersonSearchQuery>,
 ) -> Result<Json<PersonSearchResponse>, (StatusCode, Json<serde_json::Value>)> {
     let db = PostgresDb::init().await.map_err(|e| {