Refactor sidebar/home, improve tools and updates UI, and adjust helpers/tests

[DR-GRIEZEL]

• Reworked sidebar structure in src/_includes/nav.html to add a home link and move the toggle to the bottom, and updated src/_includes/navbar-pages.html to exclude the root page and remove the dashboard nav entry.
• Adjusted sidebar layout and behavior in src/assets/css/main.css including position -> sticky, sizing via flex, new .sidebar-home-link and .sidebar-bottom styles, and collapse-mode tweaks.
• Improved tools layout and semantics by updating src/html/nav/tools.md and src/assets/css/tools.css to use a responsive grid and card-style panels, and limited TradingView overview widgets in src/assets/js/tools.js by introducing TRADINGVIEW_OVERVIEW_SYMBOLS.
• Enhanced updates list UI and metadata in src/assets/css/updates.css and src/assets/js/updates.js by adding commit kind icons (getCommitKindIcon), richer leaderboard rendering (rank, name, commit count), commit icon glyphs in list items, and limiting leaderboard length to top 10.
• Removed the dashboard.html nav page, replaced references to dashboard in the AI assistant helper with the home path, and updated src/assets/js/ai-assistant.js accordingly.
• Updated unit tests in src/test/ai-assistant.test.js and src/test/updates.test.js to reflect the new reply content and added tests for getCommitKindIcon.