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/App.svelte

@@ -13,6 +13,7 @@
   import CcConnect from "./routes/CcConnect.svelte";
   import InfoEngine from "./routes/InfoEngine.svelte";
   import OPC from "./routes/OPC.svelte";
+  import Transmission from "./routes/Transmission.svelte";
   import Login from "./routes/Login.svelte";
   import { onMount } from "svelte";
   import { getToken, checkAuth, setToken, currentUser, setCurrentUser, getPreferences, savePreferences, tryRefreshSession, logout as logoutSession } from "./lib/api.js";
@@ -31,6 +32,7 @@
     "cc-connect",
     "info-engine",
     "opc",
+    "transmission",
   ]);
 
   let page = $state("dashboard");
@@ -211,6 +213,8 @@
           <InfoEngine />
         {:else if page === "opc" && hasPageAccess("opc")}
           <OPC />
+        {:else if page === "transmission" && hasPageAccess("transmission")}
+          <Transmission />
         {:else if page !== "terminal"}
           <Dashboard />
         {/if}