feat(tui): Add data handles for real-time network stats polling

Added API methods to support background RPC polling:

New Public Methods:
- get_network_stats_handle() → Arc<Mutex<NetworkStats>>
- get_live_tx_handle() → Arc<Mutex<Vec<LiveTransaction>>>

These enable background threads to update TUI data structures.

Usage Pattern:
```rust
let stats_handle = app.get_network_stats_handle();
let tx_handle = app.get_live_tx_handle();

std::thread::spawn(move || {
    loop {
        // Fetch from RPC
        let stats = fetch_network_stats(&rpc_url);
        *stats_handle.lock().unwrap() = stats;

        sleep(5 secs);
    }
});
```

Foundation Complete:
✅ NetworkStats data structure
✅ LiveTransaction data structure
✅ render_network_stats_panel() UI
✅ Thread-safe Arc<Mutex<>> handles
✅ Integrated into dashboard layout

Next: Wire up actual RPC calls in background thread

🔧 Generated with Claude Code
Co-Authored-By: Claude <[email protected]>

Author: 0xrinegade

src/utils/tui/app.rs

@@ -267,6 +267,16 @@ impl OsvmApp {
         Arc::clone(&self.ai_insights)
     }
 
+    /// Get network stats handle for background thread updates
+    pub fn get_network_stats_handle(&self) -> Arc<Mutex<NetworkStats>> {
+        Arc::clone(&self.network_stats)
+    }
+
+    /// Get live transactions handle for background thread updates
+    pub fn get_live_tx_handle(&self) -> Arc<Mutex<Vec<LiveTransaction>>> {
+        Arc::clone(&self.live_transactions)
+    }
+
     pub fn set_status(&self, status: &str) {
         *self.status.lock().unwrap() = status.to_string();
     }