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.
- Introduced asynchronous decoding for base64 image data to improve performance and responsiveness.
- Added caching for decoded image bytes to optimize loading times and reduce redundant processing.
- Updated error handling to provide clearer feedback when image loading fails, enhancing user experience.
- Refactored loading logic to streamline the process of checking cached images and managing loading states.
- Improved the handling of data URLs and relative URLs for better image attachment management.
- Updated error handling in EnhancedErrorService to utilize context for color tokens, improving theme consistency.
- Refactored various components to use context-aware shadow and color properties, enhancing visual coherence.
- Replaced hardcoded color values with dynamic tokens in multiple widgets, ensuring better adaptability to theme changes.
- Improved overall code maintainability by centralizing theme-related logic and reducing direct dependencies on static theme values.
