- Apply os.path.abspath() to all DB/session path resolution (#144)
  so relative env vars resolve against the filesystem root, not WORKDIR
- Log Telethon session DB path at INFO before client creation (#142)
  to distinguish session DB errors from main application DB errors
- Remove /app from chown in Dockerfile (#145 comment) — static code
  should not be writable at runtime; add PYTHONDONTWRITEBYTECODE=1
  and PYTHONUNBUFFERED=1
- Align entrypoint.sh path priority with Python code (DATABASE_PATH →
  DATABASE_DIR → DB_PATH → BACKUP_PATH) and resolve to absolute

Closes #142, closes #144

- Add DB_PATH env var check to src/config.py (was missing, causing
  inconsistency with db/base.py, alembic/env.py, and migrate.py)
- Fix entrypoint.sh to respect DB_PATH env var without overwriting
  a pre-set value, using intermediate _DB_FILE variable
- Add priority comment in entrypoint.sh documenting the fallback chain:
  DATABASE_PATH > DATABASE_DIR > DB_PATH > BACKUP_PATH/telegram_backup.db
- Remove stale unittest.main() from test_issue_fixes.py (pytest-style
  classes don't need it, and it would skip async tests)

The session path log is emitted in connect(), not in the create()
factory method. Tests now properly exercise the connect() path and
mock get_db_manager + RealtimeNotifier dependencies.

fix: resolve relative paths, add session log, remove /app ownership