Fix Jenkins-update flow: redeploy_project pull + delete_image safety + delete_container

Bug fixes from product test:
1. redeploy_project: BUILD_FAILED now includes explicit image pull (stop → pull → start)
2. delete_image: Distinguishes running vs stopped containers, suggests system_prune for stopped refs
3. New tool delete_container: Verify stopped state before deletion, confirmation required

Tests added for all three paths plus stopped-container edge cases.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/mcp_synology_container/modules/images.py

@@ -217,7 +217,8 @@ def register_images(mcp: FastMCP, config: AppConfig, client: DsmClient) -> None:
         img_hash = target.get("id", "")
 
         # Check if image is in use by any container
-        in_use_by: list[str] = []
+        in_use_running: list[str] = []
+        in_use_stopped: list[str] = []
         try:
             ctr_data = await client.request(
                 "SYNO.Docker.Container",
@@ -231,12 +232,25 @@ def register_images(mcp: FastMCP, config: AppConfig, client: DsmClient) -> None:
                     ctr_img_id == img_hash or (hash_prefix and ctr_img_id.startswith(hash_prefix))
                 ):
                     ctr_name = ctr.get("name") or ctr.get("Names", ["?"])[0]
-                    in_use_by.append(ctr_name)
+                    status = ctr.get("status", ctr.get("state", "")).lower()
+                    if status == "running":
+                        in_use_running.append(ctr_name)
+                    else:
+                        in_use_stopped.append(ctr_name)
         except Exception as e:
             logger.debug("Could not fetch containers for in-use check: %s", e)
 
-        if in_use_by:
-            return f"Cannot delete '{display_name}': image is used by " + ", ".join(in_use_by)
+        if in_use_running:
+            return (
+                f"Cannot delete '{display_name}': image is used by running container(s): "
+                + ", ".join(in_use_running)
+            )
+
+        if in_use_stopped:
+            return (
+                f"Cannot delete '{display_name}': image is used by stopped container '{in_use_stopped[0]}'.\n"
+                f"Delete the container first or run system_prune to clean up stopped containers."
+            )
 
         if not confirmed:
             return (