UI refinements: Send button, server deletion detection, remove manual refresh

- Rename "Order" button to "Send" throughout UI
- Detect server-side document deletions (404) and auto-archive
- Remove manual refresh button (auto-refresh handles this)
- Fix password toggle button with preventDefault/stopPropagation
- Make auto-refresh silent (no status messages)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/background/service-worker.ts

@@ -256,9 +256,12 @@ chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
         sendResponse({ success: true, ...result });
       })
       .catch(error => {
+        // Include error code for 404 detection
+        const errorCode = (error as { statusCode?: number }).statusCode;
         sendResponse({
           success: false,
-          error: error instanceof Error ? error.message : 'Failed to get status'
+          error: error instanceof Error ? error.message : 'Failed to get status',
+          errorCode
         });
       });
     return true;