feat(web): improve WASM channel setup flow (#380)

* feat(web): improve WASM channel setup flow with stepper UI and auto-configure

Streamline the WASM channel setup experience in the web gateway:

- Auto-open configure modal after installing a WASM channel
- Add progress stepper (Installed → Configured → Active) on channel cards
- Replace generic Activate button with state-specific actions (Setup, Reconfigure, Restart)
- Show "Awaiting Pairing" status for Telegram until first user is paired
- Add SSE extension_status events for real-time status updates
- Add gateway restart endpoint (POST /api/gateway/restart) with idempotency guard
- Always mount webhook routes at startup so hot-added channels work without restart
- Add pairing request polling (10s interval) on extensions tab
- Track activation errors per channel with inline error display

Includes review fixes: activation_error priority over active status, stepper
failed state rendering, restart poll timeout, configure modal double-submit
guard, and SSE sender ordering constraint documentation.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* refactor: address PR review comments

- Move PairingStore construction outside .map() loop
- Extract createReconfigureButton() helper to reduce duplication

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

tests/openai_compat_integration.rs

@@ -201,6 +201,7 @@ async fn start_test_server_with_provider(
         registry_entries: Vec::new(),
         cost_guard: None,
         startup_time: std::time::Instant::now(),
+        restart_requested: std::sync::atomic::AtomicBool::new(false),
     });
 
     let addr: SocketAddr = "127.0.0.1:0".parse().unwrap();
@@ -689,6 +690,7 @@ async fn test_no_llm_provider_returns_503() {
         registry_entries: Vec::new(),
         cost_guard: None,
         startup_time: std::time::Instant::now(),
+        restart_requested: std::sync::atomic::AtomicBool::new(false),
     });
 
     let addr: SocketAddr = "127.0.0.1:0".parse().unwrap();

tests/ws_gateway_integration.rs

@@ -59,6 +59,7 @@ async fn start_test_server() -> (
         registry_entries: Vec::new(),
         cost_guard: None,
         startup_time: std::time::Instant::now(),
+        restart_requested: std::sync::atomic::AtomicBool::new(false),
     });
 
     let addr: SocketAddr = "127.0.0.1:0".parse().unwrap();