dashboard/app: migrate to bootstrap

[tarasmadan]

dashboard/app: migrate to bootstrap

Justification

The Syzkaller dashboard currently relies on custom, vanilla CSS and JavaScript for common UI components (dropdowns, collapsible panels, tables, navigation). This leads to:

• Maintenance Overhead: We are reinventing the wheel for standard components, making the codebase harder to maintain.
• Rigid UI: The current design lacks responsiveness and modern visual standards.
• Barrier to Entry: Contributors without deep frontend experience find it difficult to make UI improvements.
  Migrating to Bootstrap 5 will allow us to delete significant amounts of custom CSS/JS, leverage a robust and responsive grid system, and utilize standard, well-tested components (cards, navs, tables, collapse) to quickly improve the user experience.
  To minimize risk and ensure easy reviews, the migration will be done in very small, incremental steps.

Migration Plan

• Phase 1: Infrastructure & Setup
  • Define head_bootstrap template (loading Bootstrap via CDN) and migrate error.html to use Bootstrap layout and alert components.
    • dashboard/app: migrate error page to bootstrap #7587
• Phase 2: Global Layout & Navigation
  • Migrate the main header navigation (templates.html:header) to Bootstrap Navbar/Navs.
    • dashboard/app: migrate header navigation to Bootstrap #7608
• Phase 3: Page-by-Page Migration
  • Migrate subsystems.html (simple table layout).
  • Migrate manager.html.
  • Migrate the main dashboard page (main.html and its sub-templates like bug_list, manager_list).
  • Migrate the bug details page (bug.html and bisect_results, crash_list).
• Phase 4: Migrate syz-manager
  • TODO
• Phase 5: Cleanup & Optimization
  • Audit and delete redundant custom styles from style.css.
  • (Optional) Switch from CDN to locally served Bootstrap assets for offline support.