test(web-e2e): never reuse another backend as the storage E2E backend

server-storage.e2e.ts deletes every playlist before each test. Reusing a
backend already listening on STORAGE_BACKEND_PORT outside CI could have
wiped a real library; an occupied port now fails the run instead.

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

apps/web-e2e/playwright.config.ts

@@ -129,7 +129,9 @@ export default defineConfig({
                 IPTVNATOR_DATA_DIR: storageBackendDataDir,
             },
             url: `http://localhost:${storageBackendPort}/health`,
-            reuseExistingServer: !process.env['CI'],
+            // Never another backend on that port: the specs delete every
+            // playlist before each test, which would wipe its library.
+            reuseExistingServer: false,
             cwd: workspaceRoot,
         },
     ],