fix(ble): keep auto-reconnect alive when the rescan fails

[eigger]

Auto-reconnect waits for an advertisement from the adapter's MAC before retrying, but that wait sat outside the retry loop's try/catch:

while (isActive) {
    waitForDevice()          // <- unguarded
    try { runObdSession(...) }
    catch (e: Exception) { ...; delay(3_000) }
}

Any failure inside waitForDevice escapes the while loop entirely, runs the finally, and terminates the connect() flow for good. Nothing is scanning after that, yet the last status emitted was Scanning, so the device sits in "scanning" forever and never reconnects — while a manual connect still works, because that path starts a fresh job with skipScan=true and dials the MAC directly instead of scanning. That matches the reported symptom exactly.

scanForMac can end without emitting (permission check returning early, or the underlying scan flow completing or erroring after Android refuses another scan start), and first() on an empty flow throws NoSuchElementException, so this is reachable in normal use rather than only on a hard error.

Move waitForDevice inside the try in both the OBD and GATT-notify loops so a scan failure is retried like any other session failure, and log the reason at LINK level so the next occurrence is visible instead of silent. Also make the missing-permission path in scanForMac throw SecurityException rather than returning an empty flow, so the cause is named instead of surfacing as an unrelated NoSuchElementException.