feat: add Transmission monitoring to dashboard

- Add backend API for Transmission RPC integration
- Create frontend page with torrent and tracker status
- Add health monitoring script
- Display daemon status, speeds, and tracker errors
- Support reannounce, start/stop actions

dashboard/frontend/src/components/Sidebar.svelte

@@ -42,6 +42,7 @@
     { label: "Jellyfin", remoteHref: "https://media.jimmygan.com:8443", icon: "play" },
     { label: "Audiobookshelf", remoteHref: "https://books.jimmygan.com:8443", icon: "headphones" },
     { label: "Immich", remoteHref: "https://photos.jimmygan.com:8443", icon: "image" },
+    { id: "transmission", label: "Transmission", icon: "download" },
   ];
 
   const defaultTools = [
@@ -254,6 +255,8 @@
       <svg class="w-[16px] h-[16px]" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="1.8"><path stroke-linecap="round" stroke-linejoin="round" d="M3 18v-6a9 9 0 0118 0v6M3 18a3 3 0 003 3h0a3 3 0 003-3v-2a3 3 0 00-3-3h0a3 3 0 00-3 3v2zm18 0a3 3 0 01-3 3h0a3 3 0 01-3-3v-2a3 3 0 013-3h0a3 3 0 013 3v2z" /></svg>
     {:else if icon === "image"}
       <svg class="w-[16px] h-[16px]" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="1.8"><path stroke-linecap="round" stroke-linejoin="round" d="M4 16l4.586-4.586a2 2 0 012.828 0L16 16m-2-2l1.586-1.586a2 2 0 012.828 0L20 14m-6-6h.01M6 20h12a2 2 0 002-2V6a2 2 0 00-2-2H6a2 2 0 00-2 2v12a2 2 0 002 2z" /></svg>
+    {:else if icon === "download"}
+      <svg class="w-[16px] h-[16px]" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="1.8"><path stroke-linecap="round" stroke-linejoin="round" d="M7 16a4 4 0 01-.88-7.903A5 5 0 1115.9 6L16 6a5 5 0 011 9.9M9 19l3 3m0 0l3-3m-3 3V10" /></svg>
     {:else if icon === "openclaw"}
       <svg class="w-[16px] h-[16px]" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="1.8"><path stroke-linecap="round" stroke-linejoin="round" d="M8 10h.01M12 10h.01M16 10h.01M9 16H5a2 2 0 01-2-2V6a2 2 0 012-2h14a2 2 0 012 2v8a2 2 0 01-2 2h-5l-5 5v-5z" /></svg>
     {:else if icon === "chat"}