chore(backend): mypy strict clean + ruff format pass

Pre-merge sanity per devops checklist (ruff format --check, mypy --strict).

Type fixes:
- ORM models: `Mapped[dict]` → `Mapped[dict[str, Any]]` (audit, scenario, run,
  report, ttp, detection.artifact_files_json). Equivalent on Pydantic DTOs
  (TtpBase.params_schema_json, ScenarioStepBase.params_override_json).
- Rename `TtpRead.current_version` → `TtpRead.version` to mirror the ORM
  column (which itself was renamed in D-009 cleanup).
- Flask blueprints: add `-> ResponseReturnValue` to every view, plus typed
  UUID params on `_validate_step_consistency`.
- `templating/filters.py`: rewrite the conditional re2 import so mypy can
  narrow the union (`ModuleType | None`); the runtime branch on `_re2 is not
  None` removes the unused-ignore that was triggered by warn_unused_ignores.
- `pyproject.toml`: add `flask_login.*` and `pythonjsonlogger.*` to the
  `[[tool.mypy.overrides]]` `ignore_missing_imports` list (both ship without
  typed marker).
- Misc: drop stale `# type: ignore` comments (`app.py:36`,
  `rbac/decorators.py:35`) flagged by `warn_unused_ignores`. Keep
  `logging.JsonFormatter` ignore because the symbol exists at runtime but is
  not re-exported through the typed surface.

Formatting:
- `ruff format` applied (15 files normalized; line-length unchanged at 100).

Verification on this commit:
- `ruff check`  → All checks passed.
- `ruff format --check` → 68 files already formatted.
- `mypy --strict src` → Success: no issues found in 54 source files.
- `pytest tests/unit` → 49 passed.

backend/src/mimic/rbac/decorators.py

@@ -4,16 +4,13 @@ from __future__ import annotations
 
 from collections.abc import Callable
 from functools import wraps
-from typing import TYPE_CHECKING, ParamSpec, TypeVar
+from typing import ParamSpec, TypeVar
 
 from flask import abort
 from flask_login import current_user
 
 from mimic.rbac.matrix import Permission
 
-if TYPE_CHECKING:
-    pass
-
 P = ParamSpec("P")
 R = TypeVar("R")
 
@@ -32,7 +29,7 @@ def require_perm(perm: Permission) -> Callable[[Callable[P, R]], Callable[P, R]]
                 abort(403)
             return view(*args, **kwargs)
 
-        return _wrapped  # type: ignore[return-value]
+        return _wrapped
 
     return _decorate