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/mcp/router.py

@@ -1,4 +1,4 @@
-"""T33 MCP Server — HTTP wrapper for SSE transport.
+"""T33 MCP Server - HTTP wrapper for SSE transport.
 
 Per v4.0 §T33. Endpoints:
   POST /mcp                  JSON-RPC 2.0 endpoint
@@ -68,7 +68,7 @@ async def jsonrpc_handler(req: JsonRpcRequest) -> dict:
                 "serverInfo": {
                     "name": "rugmunch-intelligence",
                     "version": MCP_SERVER_VERSION,
-                    "description": "Crypto intelligence platform — 13+ chains, 8 MCP tools, x402 paid tier",
+                    "description": "Crypto intelligence platform - 13+ chains, 8 MCP tools, x402 paid tier",
                 },
                 "capabilities": {"tools": {}, "resources": {}, "prompts": {}},
             },