fix: compile processing.rs + mount processing_routes

- Fix 9 compilation errors in processing.rs:
  - memory_mb typo (mem_mb)
  - download_json return type
  - Chunk from_row (use row_to_json)
  - ProgressResponse/SystemHealthInfo/ProcessorProgressInfo Deserialize
  - Remove flush_all/flush (methods don't exist)
- Add pub mod processing to api/mod.rs
- Merge processing::processing_routes() into server router

src/api/mod.rs

@@ -4,6 +4,7 @@ pub mod auth;
 pub mod docs;
 pub mod files;
 pub mod five_w1h_agent_api;
+pub mod processing;
 pub mod health;
 pub mod identities;
 pub mod identity_agent_api;