feat(db): drop users.consentGiven/consentAt (ADR-0014 step 8)

Backfills consent_given=1 rows into user_consents as data:core before
dropping the legacy columns. auth.ts now writes user_consents on signup;
POST /consent writes user_consents; admin/user routes cleaned of the old
fields. Migration is idempotent — DROP COLUMN is wrapped in try/catch so
it no-ops on fresh DBs that never had the columns.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/api/src/db/schema.ts

@@ -7,10 +7,6 @@ export const users = sqliteTable('users', {
   image: text('image'),
   googleId: text('google_id').unique(),
   role: text('role').notNull().default('user'), // 'user' | 'admin'
-  // Legacy single-bit consent. Superseded by user_consents (consent_key='data:core').
-  // Kept for one release per ADR-0014 migration plan; reads consult both, writes go to user_consents only.
-  consentGiven: integer('consent_given', { mode: 'boolean' }).notNull().default(false),
-  consentAt: text('consent_at'),
   // Stable globals (ADR-0014). Per-agent prefs land in user_preferences instead.
   tone: text('tone'),                     // 'direct' | 'gentle' | 'motivational'
   tipKindsJson: text('tip_kinds_json'),    // JSON array of allowed tip kinds; null = all