Add Riverpod-aware image header and cache manager support for network
images used in avatar and markdown widgets. Convert AvatarImage to a
ConsumerWidget and read a self-signed cache manager and HTTP headers
from Riverpod so CachedNetworkImage can send auth/custom headers and use
the provided cache manager. In Markdown image builder, obtain headers
and cache manager from a ProviderContainer (via ProviderScope.containerOf)
to enable the same authenticated loading in non-consumer contexts.
Introduce image_header_utils.dart to centralize building Authorization
and custom headers from auth/api providers, with helpers for Ref,
WidgetRef, and ProviderContainer. Add dependency adjustments in
pubspec.lock for flutter_cache_manager and http marked as direct main.
These changes ensure protected images (self-signed or auth-required)
load correctly across the app and reuse the configured cache manager.
Introduce server TTS support and engine selection while keeping
device TTS as the default.
- Add new persistence keys for storing TTS engine and selected
server voice (ttsEngine, ttsServerVoiceId, ttsServerVoiceName).
- Extend TextToSpeechService to support two engines:
TtsEngine.device (FlutterTts) and TtsEngine.server (remote audio).
- Wire in an AudioPlayer and optional ApiService to fetch raw
audio bytes from the server and play them, with event hooks
mapped to existing lifecycle callbacks.
- Implement fallback to device TTS on server errors or empty
responses, and ensure player lifecycle (pause/stop/dispose)
is handled when using server engine.
- Allow engine and preferred voice to be configured before
initialization and updated at runtime via updateSettings.
This enables selecting a server-side voice and using a remote
TTS provider while preserving compatibility with the existing
device TTS implementation.
