Add bandwidth statistics tab with live chart

- Add new Statistics tab between Downloads and Settings
- Implement real-time bandwidth chart using Canvas (60s history)
- Add session overview with 8 stats cards (speed, downloaded, files, packages, etc.)
- Add provider statistics with progress bars
- Add getSessionStats IPC endpoint
- Support dark/light theme in chart rendering

src/shared/ipc.ts

@@ -25,5 +25,6 @@ export const IPC_CHANNELS = {
   PICK_CONTAINERS: "dialog:pick-containers",
   STATE_UPDATE: "state:update",
   CLIPBOARD_DETECTED: "clipboard:detected",
-  TOGGLE_CLIPBOARD: "clipboard:toggle"
+  TOGGLE_CLIPBOARD: "clipboard:toggle",
+  GET_SESSION_STATS: "stats:get-session-stats"
 } as const;