Add Room database persistence for recommendation feedback queue

Summary

Persist recommendation feedback queue to Room database instead of in-memory storage

Background

During code review of !7 (merged), michael_usanchenko suggested persisting the feedback retry queue to Room database. Currently it's only stored in memory, so queued feedback is lost on app restart.

Requirements

• Create Room entity for feedback queue items
• Implement DAO with insert/delete/query operations
• Migrate from in-memory list to database storage
• Add WorkManager for background retry processing
• Handle database migration gracefully

Proposed Schema

@Entity(tableName = "recommendation_feedback_queue")
data class FeedbackQueueItem(
    @PrimaryKey(autoGenerate = true) val id: Long = 0,
    val recommendationId: String,
    val action: String,
    val timestamp: Long,
    val retryCount: Int = 0,
    val lastError: String? = null
)

Acceptance Criteria

• Room entity and DAO created
• Migration from in-memory to database
• WorkManager scheduled for retry processing
• Old feedback items cleaned up after 7 days
• Unit tests for database operations

Related Work

• Implemented in !7 (merged)
• Follow-up from code review discussion

Epic Context

mobile-section