[Phase 6] Create 7-Day Trial Logic and Expiry Enforcement

[VenkataAnilKumar]

Goal

Implement trial lifecycle with post-trial generation lock.

Scope

• Trial start + end timestamps per workspace
• Day 8 generation lock behavior
• In-app trial countdown and upgrade prompts
• 30-day post-cancel data retention behavior

Acceptance Criteria

• Trialing workspaces can generate within limits
• Day 8 blocks generation and prompts upgrade
• Data retention policy is enforced consistently