0.1.4

Fixes from the Operator v1 release review (MOB-395).

Changed (behaviour)

• HCE no longer serves while the phone is locked. The contributed
  res/xml/mob_nfc_hce_apduservice.xml now declares
  android:requireDeviceUnlock="true" (was "false").
• HCE emulation is foreground-only and is now stopped on background.
  When the host activity pauses (backgrounded, screen off, a permission
  prompt / dialog-style activity on top, an activity-recreating config change) the emulated payload is
  dropped, the preferred-service claim released, MobNfcApduService refuses
  every APDU (6A82), and the owner receives {:nfc, :emulation_stopped}.
  Previously only the routing preference was released and the payload was
  retained and re-armed on resume. Apps that want emulation back must call
  MobNfc.emulate_ndef/3 again, e.g. on {:mob_device, :did_become_active}.
• An emulate_ndef/3 call that passes the up-front checks (size, payload, an
  attached activity) but then fails ends any emulation already running, and a
  successful one from another process replaces it; the previous owner gets
  {:nfc, :emulation_stopped} in both cases. Reader mode is dropped only once
  emulation is actually live, so a failed emulate no longer kills a reader
  session.

Fixed

• emulate_ndef/3 no longer claims success on hardware that can't
  emulate. {:nfc, :emulation_started} is sent only when the device has
  FEATURE_NFC_HOST_CARD_EMULATION, the NFC adapter exists and is enabled,
  the activity is resumed, and CardEmulation.setPreferredService succeeded.
  Otherwise one error arrives instead: {:nfc, :error, :unavailable}
  (no NFC / no HCE / app not in the foreground / routing refused),
  {:nfc, :error, :disabled} (NFC switched off), matching start_reading/2,
  or {:nfc, :error, :no_activity} (no host activity attached yet).
• NDEF messages larger than the emulated file are rejected. The emulated
  tag advertises a 1024-byte NDEF file including the 2-byte NLEN, so
  emulate_ndef/3 now rejects messages over 1022 bytes with
  {:nfc, :error, :too_large} (checked in Elixir before the NIF, and again in
  the Android bridge). New MobNfc.Hce.max_message_size/0,
  MobNfc.Hce.check_size/1, and MobNfc.Hce.stop/1 (the pure reference for the
  stopped-service behaviour); MobNfc.Hce.new/2 raises on an oversized message.