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>

website/download.html

@@ -73,6 +73,9 @@
             <div class="changelog">
                 <div class="changelog-date">v0.3.6 &mdash; March 20, 2026</div>
                 <ul>
+                    <li><strong>Network indicator</strong> &mdash; Header shows connection status dot (black/red/yellow/green for 0/1/2-10/11+ connections) with capability labels (Public, Server).</li>
+                    <li><strong>Tab badges</strong> &mdash; Feed shows new post count, My Posts shows new engagement count, People shows online count, Messages shows unread conversation count. Numbers only, no labels.</li>
+                    <li><strong>Message read tracking</strong> &mdash; Conversations marked as read on open, close, and send. Prevents re-notification of already-seen messages.</li>
                     <li><strong>Active CDN replication</strong> &mdash; All devices proactively request replication of their recent posts (&lt;72h) to connected peers. Targets prioritized: desktops &gt; anchors &gt; phones. Graceful with small networks (1 peer = 1 replica). ReplicationRequest/Response (0xE1/0xE2) wire messages.</li>
                     <li><strong>Device roles</strong> &mdash; Nodes classified as Intermittent (phones), Available (desktops), or Persistent (anchors). Advertised in InitialExchange. Influences replication target selection and budget defaults.</li>
                     <li><strong>Bandwidth budgets</strong> &mdash; Hourly replication budget (content pulled to cache) and delivery budget (content served). Phones: 100MB/1GB, Desktops: 200MB/2GB, Anchors: 200MB/1GB. Auto-reset hourly. Blob serving declines when delivery budget exhausted.</li>