Implements user-facing content moderation by allowing authenticated users
to report posts and comments. Reports are categorized by reason (spam,
harassment, doxing, illegal content, child safety, other) with an optional
explanation field.

Changes:
- Add ReportDialog widget with type-safe ReportReason enum
- Add submitReport() API method with input validation
- Add "Report comment" option to comment overflow menu
- Add "Report post" option to post overflow menu
- Show sign-in prompt when unauthenticated users try to report

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Extract duplicated share button logic from multiple screens into a single
reusable ShareButton widget. This improves consistency and makes it easier
to implement real share functionality in the future.

Changes:
- Add ShareButton widget with IconButton and InkWell style variants
- Update ShareIcon to use ArrowShareRight from Bluesky's design system
- Replace inline share implementations in CommunityFeedScreen, PostDetailScreen,
ProfileScreen, and PostCardActions with the new ShareButton component
- Remove direct share_plus imports from individual screens (share logic
will be centralized when fully implemented)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Implement full community feed navigation allowing users to tap on community
avatars/names in post cards to view community details and browse posts.

Changes:
- Add CommunityFeedScreen with collapsing SliverAppBar and frosted glass effect
- Add Feed/About tabs with feed sorting (Hot, New, Top)
- Add getCommunity() and getCommunityFeed() API methods
- Add TappableCommunity widget for consistent navigation from post cards
- Add CommunityHeader widget matching profile header design pattern
- Add DisplayUtils for shared avatar colors and number formatting
- Add share functionality for communities
- Improve error handling with specific exception types (Network, NotFound, Server)
- Add subscribe/join button with loading states and animations

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Add comprehensive delete support for posts and comments with proper
error handling, authorization checks, and UI feedback.

Features:
- Add deleteComment method to CommentService and CommentsProvider
- Add deletePost method to CovesApiService
- Add delete menu option to CommentCard and PostCardActions (author-only)
- Use API's replyCount for accurate collapsed/continue thread counts
- Improve deleted comment display with deletion reason

Error Handling:
- Add 404 and network timeout handling to delete operations
- Fix _isDeleting flag timing to prevent race conditions
- Add specific NetworkException and NotFoundException handlers in UI
- Add haptics error handling for unsupported devices

Other:
- Add const to CommentStats constructor
- Improve deletePost docstring with exception types

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Initialize vote states from viewer data when fetching comments on user
profile pages. This ensures server scores remain authoritative and
prevents double-counting votes that were made elsewhere.

Changes:
- Add VoteProvider dependency to UserProfileProvider via ProxyProvider2
- Initialize vote states on refresh (all comments) and pagination (new only)
- Add _initializeCommentVoteState helper for flat CommentView objects
- Add debug warning when VoteProvider is unexpectedly null

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Aligns models with backend structure where content lives inside record objects.
This refactor enables proper soft-delete support while maintaining backward
compatibility through convenience getters.

Changes:
- Add PostRecord and CommentRecord classes for nested content/facets
- Add isDeleted and deletionReason fields to PostView and CommentView
- Add backward-compatible getters (content, title, text, facets)
- Update CommentCard to show [deleted] placeholder and hide vote buttons
- Add date parsing error handling with specific messages
- Add debug logging for facet parsing failures
- Type embed field properly as Map<String, dynamic>?
- Update all tests for new record structure
- Add new comment_card_test.dart with deleted comment tests

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Implement rich text facet support for displaying and creating posts and
comments with clickable links. Links in post and comment bodies are now
tappable and open in an external browser.

Changes:
- Add facet models (ByteSlice, RichTextFacet, LinkFacetFeature) with
proper UTF-8 byte indexing for cross-platform compatibility
- Add FacetDetector utility for detecting URLs in text and generating
facets with correct byte indices (handles emoji and multi-byte chars)
- Add RichTextRenderer widget that converts facets to tappable TextSpans
- Update Post and Comment models to parse facets from record['facets']
per backend API update
- Update PostCard, DetailedPostView, and CommentCard to render rich text
- Update CreatePostScreen and ReplyScreen to detect links when composing
- Update CovesApiService and CommentService to send facets to backend
- Add comprehensive test coverage for facet models, detector, and renderer
- Fix error handling in CommentCard (show snackbar on vote failure)
- Fix sign-in navigation in CommentCard

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>