Bug: Article limit enforcement on free tier

[taha-abbasi]

Sally's Spa on free tier has 10+ articles. Investigate: is the count per-site or per-account? Did old v0.4.0 raw API articles bypass the check? Fix the enforcement logic.

[taha-abbasi]

Verified fixed. Tier-based enforcement in generate route (lines 119-134): free=10, pro=30, business=150, agency=unlimited. Old v0.4.0 raw API path no longer exists — all generation goes through job queue with tier check. Sally's Spa was bumped to business tier during testing. All current sites within limits.