Merge feat/add-community-site into dev

Resolved conflict in site/extra/community/layout.js by preserving the
basePath-based routing from dev branch, which properly handles both
community site hosting (tinytorch.ai) and Netlify deployment contexts.

Also preserved the 'join' action handler from dev branch for signup flow.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

site/extra/community/layout.js

@@ -662,7 +662,7 @@
             <a href="${basePath}/dashboard.html" class="nav-icon-btn" id="navDashboardBtn" style="display: ${displayExtras};" title="Dashboard">
                 ${footprintsIcon}
             </a>
-            
+
             <a href="${basePath}/community.html" class="nav-icon-btn" id="navCommunityBtn" style="display: ${displayExtras};" title="Community">
                 ${globeIcon}
             </a>