Update Bootswatch to 3.4.1 (latest Bootstrap 3 line)

[Copilot]

Resolves #207 — bumps Bootswatch from 3.3.7 to the newest release compatible with the app's Bootstrap 3 / react-bootstrap 0.32 stack, preserving the existing theme selector.

Changes

• src/js/theme.js — runtime theme loader now targets https://cdn.jsdelivr.net/npm/bootswatch@3.4.1/${theme}/bootstrap.min.css (switched to jsDelivr; cdnjs only hosts up to 3.3.7).
• views/index.pug — initial <link id='theme'> uses the 3.4.1 jsDelivr URL.
• src/js/serviceworker.js — offline third-party cache matcher updated to //cdn.jsdelivr.net/npm/bootswatch@3.4.1/ so themes stay cached.

The theme selector is unchanged: all 16 themes exist identically in 3.4.1, so Theme.themes(), per-theme app colors, and navbar overrides remain valid.

Scope note

The absolute latest Bootswatch (5.3.x) targets Bootstrap 5. Adopting it is not a version bump — it requires migrating react-bootstrap 0.32 → 2.x (bsStyle → variant, rewritten Modal/Navbar/Panel APIs across ~31 components) and reworking BS3 grid/utility markup throughout the SPA and Pug templates. That's a separate, large migration; this PR intentionally lands the newest release that keeps the current stack intact while picking up Bootstrap 3.4.1's XSS fixes.

privacy_policy.html (standalone, pinned to Bootswatch 4.2.1) is left untouched as it's independent of the app's theming.

[benkaiser]

No, I mean update it ALL to bootstrap 5!! @copilot

[Copilot]

No, I mean update it ALL to bootstrap 5!! @copilot

Done — the app is now on Bootstrap 5 (dbbe563). I bumped react-bootstrap 0.32 → 2.10.10, moved theming to Bootswatch 5.3.3 (keeping the theme selector with the 25 BS5 themes), and migrated all ~30 react-bootstrap components to the 2.x API (bsStyle→variant, Panel→Card, MenuItem→Dropdown.Item, NavItem→Nav.Link, Label→Badge, Glyphicon→FontAwesome, Media→flex, Navbar 2.x, Modal-based bootbox) plus the corresponding BS3→BS5 CSS class updates. bootstrap.native is removed and yarn.lock was regenerated for the new tree. Webpack build and yarn --frozen-lockfile both pass.