Addresses review feedback from #81: the backup functionality depended on the sqlite3 command-line tool, which is not included in python:slim Docker images.

Changes

• Replaced subprocess with native API: Use sqlite3.Connection.backup() instead of subprocess.run(["sqlite3", ...])
• Added context managers: Ensure connections are properly closed during backup operations

Implementation

# Before: requires sqlite3 CLI tool
backup_cmd = ["sqlite3", self.db_path, f".backup {tmp_backup_path}"]
subprocess.run(backup_cmd, text=True, check=True)

# After: uses built-in Python module
with sqlite3.connect(self.db_path) as source_conn:
    with sqlite3.connect(tmp_backup_path) as backup_conn:
        source_conn.backup(backup_conn)

The sqlite3 backup API handles concurrent access safely and requires no external dependencies.

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