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/tests/integration/conftest.py

@@ -22,9 +22,7 @@ def postgres_dsn() -> Iterator[str]:
     if PostgresContainer is None:
         pytest.skip("testcontainers not installed")
     with PostgresContainer("postgres:16-alpine") as pg:
-        url = pg.get_connection_url().replace(
-            "postgresql+psycopg2", "postgresql+psycopg"
-        )
+        url = pg.get_connection_url().replace("postgresql+psycopg2", "postgresql+psycopg")
         yield url