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/workflows.rs

@@ -11,6 +11,7 @@ use crate::AppState;
 use crate::agent::{AgentEvent, PlanStepInfo};
 use crate::db::{Workflow, ExecutionLogEntry, Comment, LlmCallLogEntry};
 use crate::state::AgentState;
+use crate::template;
 use super::{ApiResult, db_err};
 
 #[derive(serde::Serialize)]
@@ -21,6 +22,8 @@ struct ReportResponse {
 #[derive(Deserialize)]
 pub struct CreateWorkflow {
     pub requirement: String,
+    #[serde(default)]
+    pub template_id: Option<String>,
 }
 
 #[derive(Deserialize)]
@@ -36,6 +39,7 @@ pub fn router(state: Arc<AppState>) -> Router {
         .route("/workflows/{id}/report", get(get_report))
         .route("/workflows/{id}/plan", get(get_plan))
         .route("/workflows/{id}/llm-calls", get(list_llm_calls))
+        .route("/templates", get(list_templates))
         .with_state(state)
 }
 
@@ -72,6 +76,7 @@ async fn create_workflow(
     state.agent_mgr.send_event(&project_id, AgentEvent::NewRequirement {
         workflow_id: workflow.id.clone(),
         requirement: workflow.requirement.clone(),
+        template_id: input.template_id,
     }).await;
 
     Ok(Json(workflow))
@@ -191,3 +196,7 @@ async fn list_llm_calls(
     .map(Json)
     .map_err(db_err)
 }
+
+async fn list_templates() -> Json<Vec<template::TemplateListItem>> {
+    Json(template::list_all_templates().await)
+}