Refactor v2

Copy these four files into src/:
  torrent.py
  client_sync.py
  client_patch.py
  mpq_patches.py

UI imports:
  from .client_sync import VerifyWorker, UpdateWorker
  from .torrent import stop_aria2c

If the UI uses optional MPQ helpers, import them from .mpq_patches.

Validated in this archive:
  - all four generated modules compile
  - clear_torrent_resume_state exists in torrent.py
  - run_aria2c exists in torrent.py
  - stop_aria2c and parse_aria_progress exist in torrent.py
  - VerifyWorker and UpdateWorker exist in client_sync.py
  - patch_exe exists in client_patch.py
  - download_mpq_patch exists in mpq_patches.py

The original supplied torrent.py referenced some names without defining/importing
them there. This refactor assigns those existing project symbols as follows:
  .mods: MODS_REGISTRY
  .config: TWEAKS_DEFAULTS, load_tweaks_config
  .client: _LOCALE_ASSERT_OFFSET, get_client_version, remove_wdb

If those names currently live in different sibling modules in your project,
change those import lines to match their actual owners.
