Patch release: remove third-party CDN dependency.

Discovered during the Chrome Web Store submission pass that URLgen.html loaded FontAwesome from cdnjs.cloudflare.com at runtime — meaning Cloudflare saw users' IPs every time the URL filter generator opened. This contradicted the privacy policy's claim of no third-party hosts beyond iNaturalist (and GitHub for explicit issue-reporter clicks).

Removed
The remote cdnjs.cloudflare.com stylesheet link from URLgen.html.
Changed
The two draw-control icons on the URL filter generator's map are now inline SVGs in URLgen.js, using currentColor so they inherit Leaflet's control styling. Zero additional payload; no font files; no remote loads.
Note on .fa-* references in content.js
Unchanged — those query iNaturalist's own page DOM (iNat already loads FontAwesome on its pages). We never needed to ship the library ourselves for those references.