Runtime config: dedicated mergeable file + restart-on so settings take effect (issue 009)

Give each settings-config runtime a mergeable config file with its own id
(runtime-config) — the previous "config" collided with modules that already own a
config directory, so ten runtimes mounted a config file no resource declared. Point
each runtime's restart-on at it, so a settings change recreates the runtime and it
re-reads the new value (needs the mesh-host container restart-on fix on
issue/009-container-restart-on). Proven: runtime-restart-on-config e2e green.

Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF

modules/ombi/module.json

@@ -50,6 +50,14 @@
         "/services/ombi/config:/config"
       ]
     },
+    {
+      "id": "runtime-config",
+      "type": "file",
+      "path": "/var/lib/mesh/ombi/config.json",
+      "mode": "0600",
+      "content": "{}\n",
+      "merge": "json"
+    },
     {
       "id": "runtime",
       "type": "container",
@@ -66,7 +74,10 @@
         "MESH_OMBI_URL": "http://127.0.0.1:3579",
         "MESH_OMBI_CONFIG_FILE": "/run/config/config.json",
         "MESH_OMBI_CONFIG_DIR": "/var/lib/ombi/config"
-      }
+      },
+      "restart-on": [
+        "runtime-config"
+      ]
     }
   ]
 }