feat: add auth guards and move legal pages to /legal
- Protected routes now redirect to timeline when not authenticated:
settings, edit-profile, create-gallery, notifications
- Moved terms, privacy, and copyright pages from /settings/* to /legal/*
so they remain publicly accessible
- Fixed logout to navigate before calling auth.logout()
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>