Remove restart infrastructure, generalize WASM channel setup (#493)

* refactor: remove restart infrastructure and generalize Telegram-specific code

Remove the gateway restart mechanism (hot-activation works, restart won't
fix activation failures) and generalize Telegram-specific hardcoded checks
so all WASM channels get equal treatment.

Part 1 - Remove restart infrastructure:
- Remove needs_restart from ActionResponse, restart_requested from GatewayState
- Remove gateway_restart_handler, /api/gateway/restart route, exit code 75
- Remove restart overlay JS/CSS (dead code - restartGateway() never called)
- Surface actual activation errors instead of suggesting restart

Part 2 - Generalize Telegram-specific code:
- Replace telegram_owner_id: Option<i64> with generic
  wasm_channel_owner_ids: HashMap<String, i64> (backwards-compatible
  via TELEGRAM_OWNER_ID env var)
- Pairing status check now applies to all active WASM channels
- All channels get 3-step stepper in web UI, remove "coming soon" note
- Remove dead setup_telegram() code (~700 lines) - Telegram's
  capabilities.json declares required_secrets, so the generic
  setup_wasm_channel() path handles it

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

* test: add Settings::set() test for wasm_channel_owner_ids

Addresses review feedback: verify that setting per-channel owner IDs
via the dotted-path Settings::set() API works correctly with the new
HashMap<String, i64> type.

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

* fix(web): refresh extension stepper after pairing approval

loadPairingRequests only refreshed the pairing section, not the
stepper status. Call loadExtensions() instead so the stepper updates
from "Awaiting Pairing" to "Active" immediately after approval.

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

@@ -201,7 +201,6 @@ 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();
@@ -690,7 +689,6 @@ 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

@@ -59,7 +59,6 @@ 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();