feat: migrate from Dolt/MySQL to SQLite for faster boot and sync

perf: use snapshot_download for faster restore on Space boot

perf: skip backup when no files changed using mtime fingerprint

fix: use upload_folder for backup (prevents 429 rate limits) and auto-create second-brain dir

fix: use correct dataset repo (agentmemory-python-data) and fix second-brain default path for Linux

Clean up legacy TS/Node files, fix Dolt backup path sync bug, and update CSP connect-src header

Initialize Hugging Face Space deployment for AgentMemory Python (clean without assets)