fix(lint): drop ruff errors from 1470 to 0 across app/ and tests/

- Exclude generated SDK (sdks/python) and operational scripts from ruff lint
- Add targeted per-file ignores for ASYNC*, S310, S603, S607, S108, S314,
  S102, PIE810, SIM102 in scripts/
- Auto-fix safe categories (I001, F401, W292, F841, PIE790, RUF100, etc.)
- Bulk-fix S110 (try-except-pass), S112 (try-except-continue), S311 (random),
  S324 (md5/sha1), S301 (pickle) and similar lint categories
- Rename N806 non-lowercase locals, including ML X/y variables preserved
  with noqa for scikit-learn conventions
- Replace urllib.request calls with httpx.AsyncClient / httpx.Client (S310)
- Wrap blocking os.path/os calls in asyncio.get_running_loop().run_in_executor
- Replace subprocess.run with asyncio.create_subprocess_exec in async contexts
- Store asyncio.create_task return values in _background_tasks set (RUF006)
- Convert hardcoded subprocess binary names to absolute paths (S607) where
  appropriate; add noqa where path is config-driven (CAST_PATH, etc.)
- Parameterize SQL queries with placeholders and add noqa for sanitized inputs
- Fix all mechanical categories: SIM102, PIE810, TC001/2/3, S108, S314, S107,
  S306, S301, N802/N815/N817, S104, S605, S501, RUF022, UP031
- Add missing 'import asyncio' where referenced but not imported (F821)
- Fix E402 module-import-not-at-top by adding '# noqa: E402' for circular-import
  safe cases and code-defined imports
- Remove hardcoded Redis password in databus_warm_cron.py; use env vars

Tests:
- Add tests/unit/core/test_ai_router.py (8 tests): model resolution, chat
  completion with mocked httpx, fallback to OpenRouter, no-provider error,
  streaming
- Add tests/unit/core/test_tracing.py (7 tests): setup_otel disabled/enabled,
  shutdown_otel, span helpers, tracing-enabled route registration
- Add tests/unit/core/test_langfuse.py (2 tests): no-env init, noop flush
- Fix tests/unit/domain/scanner/test_service.py to import from the moved
  app.domains.scanners.core.service

Result: 'ruff check .' passes with 0 errors (was 1470).
Pytest: 808 passed, 1 skipped (no regressions).

scripts/generate_provider_chains.py

@@ -7,6 +7,7 @@ The generated file is checked into git so dev installs work offline.
 Re-run this script only when the chain topology changes (new data type,
 new provider, etc.).
 """
+
 from pathlib import Path
 
 SOURCE = Path("app/databus/provider_chains.py")
@@ -26,8 +27,8 @@ def main():
     )
     body = content.split('"""', 2)[2] if '"""' in content else content
     TARGET.write_text(header + body)
-    print("wrote {} ({} bytes)".format(TARGET, TARGET.stat().st_size))
+    print(f"wrote {TARGET} ({TARGET.stat().st_size} bytes)")
 
 
 if __name__ == "__main__":
-    main()
+    main()