feat: multi-branch template scanning from git repo + manual template selection

- Rewrite template.rs to scan all remote branches via git commands
  (git fetch/branch -r/ls-tree/git show/git archive)
- Add manual template picker dropdown in CreateForm UI
- Remove sentence-transformers/embed.py from Dockerfile (separate container)
- Clean up Gitea API approach, use local git repo instead
- Add chat panel and sidebar layout improvements

src/api/mod.rs

@@ -1,3 +1,4 @@
+mod chat;
 mod kb;
 pub mod obj;
 mod projects;
@@ -31,6 +32,7 @@ pub fn router(state: Arc<AppState>) -> Router {
         .merge(timers::router(state.clone()))
         .merge(kb::router(state.clone()))
         .merge(settings::router(state.clone()))
+        .merge(chat::router(state.clone()))
         .route("/projects/{id}/files/{*path}", get(serve_project_file))
         .route("/projects/{id}/app/{*path}", any(proxy_to_service).with_state(state.clone()))
         .route("/projects/{id}/app/", any(proxy_to_service_root).with_state(state))