v0.3.6: Network indicator, tab badges, message read tracking, UI cleanup

UI:
- Network indicator dot (black/red/yellow/green) + capability labels (Public, Server)
- Tab badges: Feed (new posts), My Posts (new engagement), People (online), Messages (unread)
- Stats bar removed — contextual counts in tab labels
- Message thread popup variable scoping fix

Message read tracking:
- mark_conversation_read on popover open, close, and message send
- Prevents re-notification of already-seen messages after app restart

Network:
- Added has_public_v6(), has_upnp() getters on Network
- NetworkSummaryDto includes hasPublicV6, hasPublicV4, hasUpnp

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/tauri-app/src/lib.rs

@@ -1441,6 +1441,9 @@ struct NetworkSummaryDto {
     total_connections: usize,
     n2_distinct: usize,
     n3_distinct: usize,
+    has_public_v6: bool,
+    has_public_v4: bool,
+    has_upnp: bool,
 }
 
 #[tauri::command]
@@ -1470,6 +1473,9 @@ async fn get_network_summary(state: State<'_, AppState>) -> Result<NetworkSummar
         total_connections: conns.len(),
         n2_distinct: n2,
         n3_distinct: n3,
+        has_public_v6: node.network.has_public_v6(),
+        has_public_v4: node.network.is_anchor(),
+        has_upnp: node.network.has_upnp(),
     })
 }