feat: storage partition retention check

[bharathraj25]

Verify partitions exist up to retention horizon; auto-discover parents

Short description

• Add startup check to validate daily partitions from retention horizon to today
• Auto-discover partitioned parents in public schema with valid_to (no hardcoding)
• Clear panic with missing date range; info log of verified parents
• Robust partition bound parsing via catalog query + regex
• Add integration tests (ok and missing-day cases); format related SQL for readability

Closes #646.