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/server.rs

@@ -14,6 +14,7 @@ use super::auth;
 use super::docs;
 use super::files;
 use super::five_w1h_agent_api;
+use super::processing;
 use super::health;
 use super::identities;
 use super::identity_agent_api;
@@ -106,6 +107,7 @@ pub async fn start_server(host: &str, port: u16) -> anyhow::Result<()> {
         .merge(identity_api::identity_routes())
         .merge(agent_api::agent_routes())
         .merge(agent_search::agent_search_routes())
+        .merge(processing::processing_routes())
         .merge(identity_agent_api::identity_agent_routes())
         .merge(five_w1h_agent_api::five_w1h_agent_routes())
         .merge(media_api::bbox_routes())