feat(backend): MCP d'édition de templates (#81)

Ajoute le MCP dédié à l'édition de templates : catalogue et classification
des templates (mcp/templates.rs infrastructure + app-tauri), use cases et
provider (application/template), enforcement de la policy des tools (mod.rs,
server.rs, tools.rs), avec la parité côté chemin OpenAI-compatible
(openai_tools.rs x2).

Lots B1 (catalogue/classification), B2 (use cases/provider) et B3
(enforcement policy) livrés en un seul commit cohérent.

QA vert (seul l'échec de bind loopback #80, connu et non-régression, écarté).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

crates/app-tauri/src/state.rs

@@ -10,12 +10,13 @@ use std::path::PathBuf;
 use std::sync::{Arc, Mutex};
 
 use backend::BackendCore;
-use infrastructure::TicketToolProvider;
+use infrastructure::{TemplateToolProvider, TicketToolProvider};
 use serde::{Deserialize, Serialize};
 
 use crate::chat::ChatBridge;
 use crate::embedded_server::EmbeddedServerController;
 use crate::pty::PtyBridge;
+use crate::templates::AppTemplateToolProvider;
 use crate::tickets::AppTicketToolProvider;
 
 pub use backend::ResumeContext;
@@ -71,6 +72,14 @@ impl AppState {
                 unlink: Arc::clone(&core.unlink_issues),
                 list_sprints: Arc::clone(&core.list_sprints),
             }) as Arc<dyn TicketToolProvider>);
+        core.template_tool_binder
+            .bind(Arc::new(AppTemplateToolProvider {
+                create: Arc::clone(&core.create_template),
+                read: Arc::clone(&core.read_template),
+                list: Arc::clone(&core.list_templates),
+                update: Arc::clone(&core.update_template),
+                delete: Arc::clone(&core.delete_template),
+            }) as Arc<dyn TemplateToolProvider>);
 
         Self {
             core,