In-app download initially stalled at 7922 bytes — not the network: the phone
reaches brouter.de fully (confirmed via Termux). BalDav was not in the device's
split tunnel, so its traffic took the wrong path; fixed device-side. Over the
now-working but bursty link the fixed 30s readTimeout tripped, so the downloader
is rewritten to resume: HTTP Range (append to the .tmp, 206=resume / 200=restart),
readTimeout 60s, up to 30 retries.
Verified on device: E40_N45 (14.1 MB) downloaded by the app (done ~55s), a
cross-tile trekking route on the app-downloaded tile (44.8 km / 316 m, 1.66s)
matches the PC-pushed tile, and listTiles returns both. Remaining Stage 2 work:
the tile-selection UI.