style: clear all 23 pre-existing ruff lint errors

Master had been failing CI lint since before this PR. Knock out the
backlog so the parallel-queue PR can ship green and future PRs don't
inherit the red baseline.

Changes by category:
- UP042 (9): Migrate `class Foo(str, Enum)` to `class Foo(StrEnum)` in
  tensors/config.py (7 enums) and tensors/server/search_routes.py (2).
  Requires Python 3.11+, already enforced by `requires-python = ">=3.12"`.
- PLR2004 (3): Extract magic comparison values in comfyui_api_routes.py
  to module-level constants (_DEFAULT_STEPS, _DEFAULT_CFG, _PROMPT_LOG_TRUNCATE).
- PLW0108 (2): Inline `lambda: StubDB()` -> `StubDB` in test_server.py.
- PLR0915 (3): Add explicit `# noqa: PLR0915` to typer command bodies
  that are intentionally long (template, templates_extract, _wait_for_completion_ws).
- PLR1714 (1): `file_path.name == model or file_path.stem == model` ->
  `model in (file_path.name, file_path.stem)` in cli.py:3047.
- SIM113 (1): Use `enumerate(as_completed(futures), start=1)` for the
  completion counter in style-sweep parallel loop.
- RUF059 (1): Prefix unused tuple-unpacked vars with `_` in _run_one.
- SIM105 (1): `try: ws.close() except Exception: pass` ->
  `contextlib.suppress(Exception)` in comfyui.py.
- PLC0415 (1): Add missing `# noqa: PLC0415` to the second of two
  function-scoped tensors.config imports.

No behavior changes. All 374 tests still pass.

tests/test_server.py

@@ -1237,7 +1237,7 @@ class TestDownloadBackgroundTasks:
                 captured["api_key"] = api_key
                 return {"file_id": 42, "sha256": "deadbeef", "linked": True, "cached": True, "error": None}
 
-        monkeypatch.setattr(download_routes_module, "Database", lambda: StubDB())
+        monkeypatch.setattr(download_routes_module, "Database", StubDB)
         return captured
 
     def test_do_download_success(self, monkeypatch, tmp_path) -> None:
@@ -1397,7 +1397,7 @@ class TestDownloadBackgroundTasks:
             def register_downloaded_file(self, *args, **kwargs):
                 return {"file_id": None, "sha256": None, "linked": False, "cached": False, "error": "boom"}
 
-        monkeypatch.setattr(download_routes, "Database", lambda: FailingDB())
+        monkeypatch.setattr(download_routes, "Database", FailingDB)
 
         dest_path = tmp_path / "model.safetensors"
         _do_download(12345, dest_path, None, download_id, {"id": 1, "modelId": 1})