chore: wechat end-to-end smoke script

Wires the existing pieces together into a runnable integration check:
scrape ~10 WeChat friends + ~50 of their messages (last 7 days) from the
real yunke CRM (read-only), upsert into a local SQLite smoke DB, then
print a summary that verifies rows landed.

Two auth modes:
* Existing-session (preferred): YK_USERID/YK_COMPANY[/YK_COOKIE] -> YunkeClient
  constructed from a captured session, login bypassed.
* Login mode (Phase-0 blocked): YUNKE_USERNAME/YUNKE_PASSWORD -> attempts
  client.login(), which the real CRM will reject until the placeholder
  password encryption is replaced. Prints a clear message and exits 3.

build_client_from_env() is split out as a pure, network-free helper so
auth-mode selection is unit-testable. main() is async (asyncio.run in
__main__). HTTPStatusError from a 401/expired session is wrapped into a
helpful message + exit 4 (no traceback). client.aclose() + engine.dispose()
always run in finally.

Defaults to SMOKE_DB_URL=sqlite+aiosqlite:///./smoke.db so no MySQL is
required. Run from yunke-server/ with the venv active:

    python -m scripts.smoke_wechat

Tests cover the entrypoint shape and auth-mode selection (no network).
Suite: 77 -> 87 passing.

Co-Authored-By: Claude <noreply@anthropic.com>

yunke-server/scripts/__init__.py

@@ -0,0 +1,7 @@
+"""Operational scripts for the yunke data mirror.
+
+Each module under this package is a standalone, runnable integration check or
+maintenance helper (e.g. the Task 1.9 smoke script). Importing this package has
+no side effects — the scripts are entry-point functions meant to be invoked via
+``python -m scripts.<name>`` from the ``yunke-server/`` directory.
+"""