feat: sync all BRAIN mobile changes - onboarding, cookies, legal, mobile UX, settings
- Add OnboardingWizard, BetaBanner, CookieBanner components
- Add legal pages (Privacy, Terms, Cookies)
- Update Layout with mobile topbar, sidebar drawer, plan banner
- Update SettingsPage with profile, API config, security
- Update CharacterForm with topic suggestions, niche chips
- Update EditorialCalendar with shared strategy card
- Update ContentPage with narrative technique + brief
- Update SocialAccounts with 4 platforms and token guides
- Fix CSS button color inheritance, mobile responsive
- Add backup script
- Update .gitignore for pgdata and backups
Co-Authored-By: Claude (BRAIN/StackOS) <noreply@anthropic.com>
2ca8b957e9