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>

frontend/style.css

@@ -2,8 +2,16 @@
 select option { color: #000 !important; }
 body { font-family: system-ui, sans-serif; max-width: 640px; margin: 0 auto; padding: 1rem; background: #1a1a2e; color: #e0e0e0; color-scheme: dark; }
 header { border-bottom: 1px solid #333; padding-bottom: 0.5rem; margin-bottom: 1rem; }
-header h1 { font-size: 1.4rem; color: #7fdbca; }
-#stats-bar { font-size: 0.8rem; color: #bbc; margin-top: 0.25rem; }
+#header-row { display: flex; justify-content: space-between; align-items: center; }
+header h1 { font-size: 1.4rem; color: #7fdbca; margin: 0; }
+#net-indicator { display: flex; align-items: center; gap: 0.4rem; }
+#net-dot { width: 10px; height: 10px; border-radius: 50%; background: #222; border: 1px solid #444; }
+#net-dot.net-black { background: #222; }
+#net-dot.net-red { background: #e74c3c; }
+#net-dot.net-yellow { background: #f1c40f; }
+#net-dot.net-green { background: #22c55e; }
+#net-labels { font-size: 0.65rem; color: #888; display: flex; gap: 0.3rem; }
+.net-label { background: #2a2a40; padding: 0.1rem 0.35rem; border-radius: 3px; color: #aab; }
 
 /* Setup overlay */
 .overlay { position: fixed; top: 0; left: 0; right: 0; bottom: 0; background: rgba(10, 10, 20, 0.92); display: flex; align-items: center; justify-content: center; z-index: 200; }