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/health_monitor.py

@@ -59,7 +59,7 @@ def _load_cooldown_state():
             with open(state_file) as f:
                 return json.load(f)
     except Exception:
-        pass
+        logging.getLogger(__name__).warning("swallowed exception", exc_info=True)
     return {}
 
 
@@ -70,7 +70,7 @@ def _save_cooldown_state(state: dict):
         with open(state_file, "w") as f:
             json.dump(state, f)
     except Exception:
-        pass
+        logging.getLogger(__name__).warning("swallowed exception", exc_info=True)
 
 
 def _should_alert(service: str) -> bool:
@@ -209,7 +209,9 @@ def send_alert(results: list):
             headers={"Content-Type": "application/json"},
         )
         with urllib.request.urlopen(req, timeout=10) as resp:
-            logger.info(f"Alert sent to webhook: HTTP {resp.status} - {len(alertable)} services down")
+            logger.info(
+                f"Alert sent to webhook: HTTP {resp.status} - {len(alertable)} services down"
+            )
     except Exception as e:
         logger.error(f"Failed to send alert to webhook: {e}")
 
@@ -269,7 +271,7 @@ def _load_prev_state():
             with open(state_file) as f:
                 return json.load(f)
     except Exception:
-        pass
+        logging.getLogger(__name__).warning("swallowed exception", exc_info=True)
     return {}
 
 
@@ -280,7 +282,7 @@ def _save_prev_state(state: dict):
         with open(state_file, "w") as f:
             json.dump(state, f)
     except Exception:
-        pass
+        logging.getLogger(__name__).warning("swallowed exception", exc_info=True)
 
 
 # ── Main ────────────────────────────────────────────────────────────
@@ -313,7 +315,9 @@ def main():
     REDIS_HOST = os.getenv("REDIS_HOST", "localhost")
     REDIS_PORT = int(os.getenv("REDIS_PORT", "6379"))
     REDIS_PASSWORD = os.getenv("REDIS_PASSWORD", "")
-    BASE_WORKER_URL = os.getenv("BASE_WORKER_URL", "http://localhost:8000/api/v1/x402/fallback/status")
+    BASE_WORKER_URL = os.getenv(
+        "BASE_WORKER_URL", "http://localhost:8000/api/v1/x402/fallback/status"
+    )
     SOLANA_WORKER_URL = os.getenv("SOLANA_WORKER_URL", "")
 
     logger.info("Running health checks...")