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/core/chunk/mod.rs

@@ -6,7 +6,6 @@ pub mod types;
 
 pub use rule1_ingest::execute_rule1;
 pub use rule3_ingest::ingest_rule3;
-pub use trace_ingest::ingest_traces;
 pub use splitter::{AsrSegment, ChunkSplitter};
 pub use trace_ingest::ingest_traces;
 pub use types::{Chunk, ChunkType};