fix(whatsapp,roles): self-heal legacy whatsapp_log schema; map underscore role aliases

CT115 (Mumuni relay #747) — two live-instance defects after PR #12:

1. GET /api/whatsapp/mock-log 500'd with a valid admin token:
   'no such column: whatsapp_log.message_text'. The model gained
   message_text/wa_message_id/ticket_number (and dropped command) in
   4afdc36 with no migration, so legacy DBs keep the (command, ...) shape.
   ensure_legacy_schema (startup, app/main.py) now adds the three missing
   columns idempotently and backfills legacy command bodies into
   message_text before dropping the obsolete NOT NULL command column, so
   both the mock-log read path and the ORM write path work on healed DBs.
   New producer/consumer regression (tests/test_whatsapp_log_legacy_heal.py)
   reproduces the exact OperationalError, then asserts 200 + data.

2. ROLE_ALIASES gap: underscore legacy roles (cs_rep, cs_manager,
   fm_dispatcher) were not mapped, so normalize_legacy_user_roles could not
   converge rows like user 18 (test@denya.com, role 'cs_rep') and the
   frontend stranded them on /tickets. Added the underscore aliases; tests
   assert normalize_role('cs_rep') == 'CS Rep' and a cs_rep row converges
   and authenticates.

tests/test_p0_auth_admin_batch.py

@@ -308,6 +308,43 @@ async def test_normalize_does_not_map_ambiguous_admin_alias(client: AsyncClient)
     assert user.role == "admin"
 
 
+async def test_underscore_legacy_aliases_normalize_to_canonical():
+    """Open-register rows can carry underscore role forms ('cs_rep',
+    'cs_manager', 'fm_dispatcher') — the exact gap Mumuni relay #747 found on
+    user 18 (test@denya.com).  Each must map onto its canonical role so startup
+    normalization can converge the row instead of stranding it on /tickets."""
+    from app.core.roles import normalize_role
+
+    assert normalize_role("cs_rep") == "CS Rep"
+    assert normalize_role("cs_manager") == "CS Manager"
+    assert normalize_role("fm_dispatcher") == "FM Dispatcher"
+    # Matching is case/whitespace tolerant, like the space-form aliases.
+    assert normalize_role(" CS_REP ") == "CS Rep"
+    assert normalize_role("cs_rep") is not None  # known, not fail-closed
+
+
+async def test_legacy_cs_rep_row_converges_and_authenticates(client: AsyncClient):
+    """A 'cs_rep' row (user 18 test@denya.com shape) is converged to canonical
+    'CS Rep' by the startup self-heal and can log in again (no fail-closed
+    denial, and the frontend CS nav sees the canonical role)."""
+    await _insert_user("cs-rep-legacy@example.com", "cs_rep")
+    await _normalize_roles()  # what lifespan does each boot
+
+    async with async_session_factory() as session:
+        from sqlalchemy import select
+        user = (
+            await session.execute(select(User).where(User.email == "cs-rep-legacy@example.com"))
+        ).scalar_one()
+    assert user.role == "CS Rep"
+
+    login = await client.post(
+        "/api/auth/login", json={"email": "cs-rep-legacy@example.com", "password": "denya123"}
+    )
+    assert login.status_code == 200, login.text
+    me = await client.get("/api/auth/me", headers=_auth(login.json()["access_token"]))
+    assert me.json()["role"] == "CS Rep"
+
+
 # ── P0 email normalization (legacy mixed-case rows) ───────────────────
 async def test_legacy_mixed_case_email_migrated_and_authenticates(client: AsyncClient):
     """A legacy row whose email was stored verbatim in mixed case (the old open