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/gcloud_multi.py

@@ -1,7 +1,7 @@
 """
 Multi-Account Google Cloud Manager
 ====================================
-Drop service account JSON files into /root/.secrets/google/ —
+Drop service account JSON files into /root/.secrets/google/ -
 the system auto-discovers them, manages tokens, and provides
 unified access across all accounts. No console needed ever again.
 
@@ -172,7 +172,7 @@ class MultiCloudManager:
             ordered = sorted(ordered, key=lambda a: 0 if a.project_id == preferred_project else 1)
 
         for acc in ordered:
-            if acc.project_id == "cryptorugmunch":  # Primary — always try first
+            if acc.project_id == "cryptorugmunch":  # Primary - always try first
                 vecs = await acc.embed_vertex(texts)
                 if vecs:
                     return vecs, acc.project_id