fix(logging): replace structlog with stdlib logging to prevent broken pipe crashes

structlog fails with BrokenPipeError when stdout is redirected (e.g., background
processes, Docker logs). Replace all structlog.get_logger() calls with
logging.getLogger() and convert keyword-style log calls to %-format strings.

Also removes stale Docs/tasks.md (2028 lines) and updates Robot Framework
tests to match current API behavior.

src/server/services/scan_service.py

@@ -225,7 +225,7 @@ class ScanService:
         scan_progress = ScanProgress(scan_id)
         self._current_scan = scan_progress
 
-        logger.info("Starting library scan", scan_id=scan_id)
+        logger.info("Starting library scan scan_id=%s", scan_id)
 
         # Start progress tracking
         try: