Covers double-upload fix (two-phase DB write + hash advisory lock), parallel account processing (remove TDLib mutex), and per-account Premium 4GB upload limit with automatic is_premium detection. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>