Map tiles: new lib/tileCache.ts (Dexie SkateSpotsTilesDB, bounded to ~3000
tiles) and lib/cachedTileLayer.ts, a Leaflet TileLayer that reads through it
(cached -> fetch+cache -> plain URL fallback). Wired into both maps (SpotMap,
RouteDialog). Chosen over a service worker so it works in the Capacitor
WebView too, where a SW never sees tile requests.
Photos: useUploadFile drops from three Blossom hosts to two and records
['fallback', '<mirror>/<sha256>']. BlossomUploader signs once and Promise.any
PUTs to every server in parallel, so the old three-host list was triple-
uploading every photo (the 'tries them in order' comment was wrong). Read
side: lib/imageFallback.ts derives same-hash mirrors and ImageWithFallback
retries them before showing the placeholder - one choke point for ~20 photo
call sites, so a dead host no longer blanks a spot.
