fix(server-storage): keep URL favorites, flush before moving, cache-full and cut-off bodies

- Moving M3U favorites keeps URL favorites and anything the server cannot
  resolve; only older channel ids are translated.
- Queued user-data edits are sent before the move writes combined values.
- A re-read that does not fit the cache keeps the old cache and baseline
  together.
- A response body cut off after its headers counts as offline.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/services/src/lib/server-storage/server-api-client.ts

@@ -107,7 +107,27 @@ export class ServerApiClient {
     }
 
     async getJson<T>(path: string): Promise<T> {
-        return (await this.request(path)).json() as Promise<T>;
+        return this.readJson<T>(await this.request(path));
+    }
+
+    /**
+     * A body cut off after the headers arrived is an outage too; malformed
+     * JSON is not.
+     */
+    async readJson<T>(response: Response): Promise<T> {
+        try {
+            return (await response.json()) as T;
+        } catch (error) {
+            if (error instanceof SyntaxError) {
+                throw error;
+            }
+            this.options.status.reportOffline();
+            throw new ServerApiError(
+                0,
+                'network',
+                'The server is not reachable.'
+            );
+        }
     }
 
     sendJson(