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/bubble_maps.py

@@ -31,6 +31,7 @@ OUR SOLUTIONS:
 import json
 from dataclasses import dataclass, field
 from datetime import datetime, timedelta
+from typing import ClassVar
 
 import numpy as np
 
@@ -165,8 +166,7 @@ class BubbleMapsPro:
     """
 
     # Node type colors
-    TYPE_COLORS: ClassVar[dict] =
-{
+    TYPE_COLORS: ClassVar[dict] ={
         "center": "#ff6b6b",
         "scammer": "#ff0000",
         "suspected_scammer": "#ff6b6b",
@@ -179,8 +179,7 @@ class BubbleMapsPro:
     }
 
     # Risk colors (gradient)
-    RISK_COLORS: ClassVar[dict] =
-{
+    RISK_COLORS: ClassVar[dict] ={
         "safe": "#00ff00",
         "low": "#90ee90",
         "medium": "#ffd700",