feat: complete browser extensions + token auth for history/admin APIs
- Extensions: rewrite both Chrome MV3 & Firefox MV2 with reliable
chrome.history.search incremental pull (not onVisited), local search-engine
filtering, URL dedup, 30s alarm, retry queue, Bearer token header
- Add icons (16/48/96/128) for both browsers
- Manifest fixes: chrome action popup, firefox options_ui + browser shim
- history-server: require NAVI_SYNC_TOKEN for POST /sync & GET history,
NAVI_ADMIN_TOKEN for DELETE; fix RWMutex deadlock (unlock before
sortDashyFavorites) that stalled syncs with valid token
- admin-server: require NAVI_ADMIN_TOKEN for item add/delete writes
f0b318be45