feat: GitHub Event Scanner - Echtzeit-Monitoring öffentlicher Pushes

- Neuer GitHubEventScannerService (BackgroundService)
  - Pollt /events API alle 30s, filtert PushEvents
  - Lädt Head-Commit-Diffs, scannt nach Key-Patterns
  - Ringbuffer (10k IDs) für Event-Deduplication
  - Gefundene Keys werden sofort geprüft (AnthropicKeyChecker)
  - Rate-Limit-Handling (403/429 → Pause bis Reset)
- Feature-Toggle in Server-Einstellungen (GitHubEventScanner)
- Status-Endpoint + Log-Endpoint (/api/admin/api-keys/event-scanner/*)
- Live-Status in API-Keys-Seite mit klappbarem Log
- Auto-Refresh alle 30s
- Plans/ in .gitignore

Endpoints/ApiKeysEndpoint.cs

@@ -34,6 +34,10 @@ public static class ApiKeysEndpoint
         app.MapPost("/api/admin/api-keys/scanned/{id}/adopt", HandleAdopt);
         app.MapDelete("/api/admin/api-keys/scanned/{id}", HandleDeleteScanned);
 
+        // Event Scanner Status & Log
+        app.MapGet("/api/admin/api-keys/event-scanner/status", HandleEventScannerStatus);
+        app.MapGet("/api/admin/api-keys/event-scanner/log", HandleEventScannerLog);
+
         // User-Endpoints (für alle authentifizierten User)
         app.MapGet("/api/api-keys/available", HandleGetAvailable);
         app.MapPut("/api/api-keys/select/{keyId}", HandleSelectKey);
@@ -466,4 +470,28 @@ public static class ApiKeysEndpoint
         });
     }
 
+    private static async Task HandleEventScannerStatus(HttpContext ctx, GitHubEventScannerService scanner)
+    {
+        if (!ctx.IsAdmin()) { ctx.Response.StatusCode = 403; return; }
+
+        await ctx.Response.WriteAsJsonAsync(new
+        {
+            enabled = scanner.Enabled,
+            running = scanner.IsRunning,
+            lastPoll = scanner.LastPoll,
+            eventsPerHour = scanner.EventsPerHour,
+            keysFoundTotal = scanner.KeysFoundTotal,
+            pollCount = scanner.PollCount,
+            lastError = scanner.LastError
+        });
+    }
+
+    private static async Task HandleEventScannerLog(HttpContext ctx, GitHubEventScannerService scanner)
+    {
+        if (!ctx.IsAdmin()) { ctx.Response.StatusCode = 403; return; }
+
+        var log = scanner.GetLog();
+        await ctx.Response.WriteAsJsonAsync(new { entries = log.Select(e => new { e.Time, e.Type, e.Message }) });
+    }
+
 }