Featured rotation -> day-slot booking: 10 slots/day, pick your start day, live occupancy

- Per-day occupancy shown in composer (Today 1/10, Tomorrow 2/10, …), full days unpickable
- Book a specific start day + duration; every covered day must have an open slot
- Slot cap turns dilution disclosure into a hard ceiling; featured skips frame-check (new-tab)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

db.js

@@ -115,6 +115,7 @@ async function bootstrap() {
   await alterSafe('ALTER TABLE campaigns ADD COLUMN nas_ad_id INT NULL');          // syndicated NAS sponsorads.ID
   await alterSafe('ALTER TABLE campaigns ADD COLUMN nas_served INT NOT NULL DEFAULT 0'); // NAS impressions already reconciled into spend
   await alterSafe('ALTER TABLE campaigns ADD COLUMN expires BIGINT NULL'); // featured rotation end time
+  await alterSafe('ALTER TABLE campaigns ADD COLUMN starts BIGINT NULL');  // featured run start (booked day)
   await q(`CREATE TABLE IF NOT EXISTS sponsor_messages (
     id INT AUTO_INCREMENT PRIMARY KEY,
     from_member INT NOT NULL,