feat: causal lab - bouton Mettre a jour + PATCH endpoint

- TabEditor: updateExisting() + bouton bleu visible si templateId set
- Bouton Creer renomme en copie pour clarifier
- PATCH /api/causal-lab/template/{id} pour graph_json + metadonnees

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/causal_lab.py

@@ -402,6 +402,41 @@ def create_template(body: CreateTemplateRequest):
         raise HTTPException(500, str(e))
 
 
+@router.patch("/api/causal-lab/template/{template_id}")
+def patch_template(template_id: int, body: dict):
+    """Met à jour un template existant en entier (graph_json, métadonnées, coefficients)."""
+    try:
+        from services.database import get_conn
+        from services.causal_graphs import get_template
+        conn = get_conn()
+        tmpl = get_template(conn, template_id)
+        if not tmpl:
+            conn.close(); raise HTTPException(404, "Template introuvable")
+
+        sets, params = [], []
+        for field in ("name", "category", "sub_type", "description", "ai_rationale"):
+            if field in body:
+                sets.append(f"{field}=?"); params.append(body[field])
+        if "instruments" in body:
+            sets.append("instruments=?"); params.append(json.dumps(body["instruments"]))
+        if "graph_json" in body:
+            sets.append("graph_json=?"); params.append(json.dumps(body["graph_json"]))
+
+        if not sets:
+            conn.close(); return {"ok": True}
+
+        sets.append("updated_at=datetime('now')")
+        params.append(template_id)
+        conn.execute(f"UPDATE causal_graph_templates SET {', '.join(sets)} WHERE id=?", params)
+        conn.commit(); conn.close()
+        return {"ok": True}
+    except HTTPException:
+        raise
+    except Exception as e:
+        logger.error(f"[causal_lab] patch_template {template_id}: {e}")
+        raise HTTPException(500, str(e))
+
+
 @router.delete("/api/causal-lab/template/{template_id}")
 def delete_template(template_id: int):
     """Supprime un template utilisateur (les templates system sont protégés)."""