feat(#532): add CommentSection component with full test coverage

[olaayoade27-coder]

Summary

Closes #532

Implements the CommentSection component and increases test coverage as required.

Changes

New: src/components/mobile/CommentSection.tsx

• Fetches comments via GET /api/{resourceType}s/{resourceId}/comments
• Post new comment via POST with input cleared on success
• Optimistic like/unlike toggle with automatic revert on API failure
• Owner-only delete (checked by authorId vs currentUserId)
• Loading spinner, empty state, error banner with Retry
• Full accessibility labels on all interactive elements

New: tests/components/CommentSection.test.tsx

30 tests across 7 suites:

• Loading state — shows/hides spinner
• Rendering — comments, author names, count heading, empty state, correct API path per resource type
• Input visibility — shown only when currentUserId is provided
• Posting — POST call, list prepend, input clear, empty/whitespace guard, error banner
• Liking — optimistic increment, optimistic decrement, revert on failure
• Deleting — owner-only button, removes from list, DELETE call
• Accessibility — all accessibilityLabel values verified

Modified: src/components/mobile/index.ts

• Exported CommentSection from the mobile component barrel

Acceptance Criteria

• Comment Section properly implements Test Coverage Increase
• All related tests pass
• No regression in existing functionality
• Code follows project coding standards
• Accessibility guidelines are followed
• Security considerations addressed (owner-only delete, input trimming)

[RUKAYAT-CODER]

This PR is not linked to any issue. kindly link this PR to the issue number