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/application/tests/template_usecases.rs

@@ -18,8 +18,8 @@ use uuid::Uuid;
 
 use application::{
     CreateAgentFromTemplate, CreateAgentFromTemplateInput, CreateTemplate, CreateTemplateInput,
-    DetectAgentDrift, DetectAgentDriftInput, SyncAgentWithTemplate, SyncAgentWithTemplateInput,
-    UpdateTemplate, UpdateTemplateInput,
+    DetectAgentDrift, DetectAgentDriftInput, ReadTemplate, ReadTemplateInput,
+    SyncAgentWithTemplate, SyncAgentWithTemplateInput, UpdateTemplate, UpdateTemplateInput,
 };
 
 // ---------------------------------------------------------------------------
@@ -224,6 +224,29 @@ async fn create_template_starts_at_initial_version() {
     assert_eq!(store.list().await.unwrap().len(), 1);
 }
 
+#[tokio::test]
+async fn read_template_returns_one_template_or_not_found() {
+    let existing = template(tid(7), "Base", "body", 3);
+    let store = FakeTemplates::with(vec![existing.clone()]);
+    let read = ReadTemplate::new(Arc::new(store));
+
+    let out = read
+        .execute(ReadTemplateInput {
+            template_id: existing.id,
+        })
+        .await
+        .unwrap();
+    assert_eq!(out.template, existing);
+
+    let err = read
+        .execute(ReadTemplateInput {
+            template_id: tid(8),
+        })
+        .await
+        .expect_err("unknown template should be not found");
+    assert_eq!(err.code(), "NOT_FOUND");
+}
+
 #[tokio::test]
 async fn update_template_bumps_version_and_publishes_event() {
     let store = FakeTemplates::with(vec![template(tid(1), "T", "v1", 1)]);