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/identities.rs

@@ -29,7 +29,7 @@ pub struct CreateIdentityResponse {
     pub quality_avg: Option<f64>,
 }
 
-pub fn identity_routes() -> Router<crate::api::server::AppState> {
+pub fn identity_routes() -> Router<crate::api::types::AppState> {
     Router::new()
         .route("/api/v1/identities", get(list_identities))
         .route("/api/v1/identity", post(create_identity))
@@ -39,7 +39,7 @@ pub fn identity_routes() -> Router<crate::api::server::AppState> {
 /// Register a Global Identity from face.json with multi-angle reference vectors.
 /// Calls select_face_reference_vectors_v2.py for automatic reference selection.
 async fn create_identity(
-    State(_state): State<crate::api::server::AppState>,
+    State(_state): State<crate::api::types::AppState>,
     Json(req): Json<CreateIdentityRequest>,
 ) -> Result<Json<CreateIdentityResponse>, (StatusCode, String)> {
     let schema = req.schema.unwrap_or("dev".to_string());
@@ -147,7 +147,7 @@ async fn create_identity(
 
 /// List all global identities
 async fn list_identities(
-    State(_state): State<crate::api::server::AppState>,
+    State(_state): State<crate::api::types::AppState>,
     Query(query): Query<ListIdentitiesQuery>,
 ) -> Result<Json<IdentityListResponse>, (StatusCode, String)> {
     let db = match PostgresDb::init().await {