style(rmi-backend): complete lint cleanup — 1175→0 ruff errors

- Fix 71 invalid-syntax files (class-body newline-broken assignments)
- Add from/None chain to 307 B904 raise-without-from sites
- Add B008 ignore to ruff.toml (already in pyproject.toml)
- Noqa F401 on __init__.py re-exports (137 sites)
- Noqa E402 on deferred imports (63 sites)
- Bulk-add stdlib/FastAPI/project imports for F821 (127 sites)
- Replace ×→x, –→-, …→... in docstrings (4093 chars)
- Manual refactor of 5 SIM103/SIM116 patterns

Tests: 791 passed (66 deselected due to pre-existing Redis issues in test_rag.py)
Co-authored-by: opencode <opencode@rugmunch.io>

app/api/v1/auth/__init__.py

@@ -1,4 +1,4 @@
-"""Authenticated routes — JWT required.
+"""Authenticated routes - JWT required.
 
 Target: portfolio, alerts, intel feeds, profile, settings.
 """

app/api/v1/auth/alerts.py

@@ -1,4 +1,4 @@
-"""Auth alerts router — /api/v1/alerts/*.
+"""Auth alerts router - /api/v1/alerts/*.
 
 Stub implementation for the alerts domain. Real implementations
 will wire up to user-configured alert rules and notification channels
@@ -52,7 +52,7 @@ async def create_alert(rule: AlertRule) -> dict[str, str]:
     """
     raise HTTPException(
         status_code=501,
-        detail="Alert persistence not yet implemented — coming in v5.1",
+        detail="Alert persistence not yet implemented - coming in v5.1",
     )
 
 
@@ -61,5 +61,5 @@ async def delete_alert(rule_id: str) -> dict[str, str]:
     """Delete an alert rule by ID."""
     raise HTTPException(
         status_code=501,
-        detail="Alert persistence not yet implemented — coming in v5.1",
+        detail="Alert persistence not yet implemented - coming in v5.1",
     )