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/timer.rs

@@ -68,6 +68,7 @@ async fn check_timers(pool: &SqlitePool, agent_mgr: &Arc<AgentManager>) -> anyho
         agent_mgr.send_event(&timer.project_id, AgentEvent::NewRequirement {
             workflow_id,
             requirement: timer.requirement.clone(),
+            template_id: None,
         }).await;
     }