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/trace_agent_api.rs

@@ -9,7 +9,7 @@ use serde::{Deserialize, Serialize};
 
 use crate::core::db::PostgresDb;
 
-pub fn trace_agent_routes() -> Router<crate::api::server::AppState> {
+pub fn trace_agent_routes() -> Router<crate::api::types::AppState> {
     Router::new()
         .route("/api/v1/file/:file_uuid/traces", post(list_traces_sorted))
         .route(
@@ -55,7 +55,7 @@ struct TracesResponse {
 }
 
 async fn list_traces_sorted(
-    State(state): State<crate::api::server::AppState>,
+    State(state): State<crate::api::types::AppState>,
     Path(file_uuid): Path<String>,
     Json(req): Json<TracesRequest>,
 ) -> Result<Json<TracesResponse>, (StatusCode, String)> {
@@ -202,7 +202,7 @@ fn lerp_i32(a: Option<i32>, b: Option<i32>, t: f64) -> Option<i32> {
 }
 
 async fn list_trace_faces(
-    State(state): State<crate::api::server::AppState>,
+    State(state): State<crate::api::types::AppState>,
     Path((file_uuid, trace_id)): Path<(String, i32)>,
     Query(q): Query<TraceFacesQuery>,
 ) -> Result<Json<TraceFacesResponse>, (StatusCode, String)> {