feat(api): add REST API with 45+ endpoints

- Add workers API for pool management
- Add jobs API for queue operations
- Add scan-rules API for CRUD operations
- Add scanner API for control and status
- Add settings API for configuration management
- Add system API for resource monitoring
- Add filesystem API for path browsing
- Add setup wizard API endpoint

backend/api/filesystem.py

@@ -0,0 +1,113 @@
+"""Filesystem browsing API for path selection."""
+import logging
+import os
+from typing import List, Optional
+from fastapi import APIRouter, HTTPException, status
+from pydantic import BaseModel
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/api/filesystem", tags=["filesystem"])
+
+
+class DirectoryItem(BaseModel):
+    """Directory item information."""
+    name: str
+    path: str
+    is_directory: bool
+    is_readable: bool
+
+
+class DirectoryListingResponse(BaseModel):
+    """Directory listing response."""
+    current_path: str
+    parent_path: Optional[str] = None
+    items: List[DirectoryItem]
+
+
+@router.get("/browse", response_model=DirectoryListingResponse)
+async def browse_directory(path: str = "/"):
+    """Browse filesystem directory."""
+    try:
+        path = os.path.abspath(path)
+
+        if not os.path.exists(path):
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"Path does not exist: {path}"
+            )
+
+        if not os.path.isdir(path):
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail=f"Path is not a directory: {path}"
+            )
+
+        parent_path = os.path.dirname(path) if path != "/" else None
+
+        items = []
+        try:
+            entries = os.listdir(path)
+            entries.sort()
+
+            for entry in entries:
+                entry_path = os.path.join(path, entry)
+
+                try:
+                    is_dir = os.path.isdir(entry_path)
+                    is_readable = os.access(entry_path, os.R_OK)
+
+                    if is_dir:
+                        items.append(DirectoryItem(
+                            name=entry,
+                            path=entry_path,
+                            is_directory=True,
+                            is_readable=is_readable
+                        ))
+                except (PermissionError, OSError) as e:
+                    logger.debug(f"Cannot access {entry_path}: {e}")
+                    continue
+
+        except PermissionError:
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail=f"Permission denied: {path}"
+            )
+
+        return DirectoryListingResponse(
+            current_path=path,
+            parent_path=parent_path,
+            items=items
+        )
+
+    except HTTPException:
+        raise
+    except Exception as e:
+        logger.error(f"Error browsing directory {path}: {e}")
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail=f"Error browsing directory: {str(e)}"
+        )
+
+
+@router.get("/common-paths", response_model=List[DirectoryItem])
+async def get_common_paths():
+    """Get list of common starting paths."""
+    common_paths = ["/", "/home", "/media", "/mnt", "/opt", "/srv", "/var", "/tmp"]
+
+    items = []
+    for path in common_paths:
+        if os.path.exists(path) and os.path.isdir(path):
+            try:
+                is_readable = os.access(path, os.R_OK)
+                items.append(DirectoryItem(
+                    name=path,
+                    path=path,
+                    is_directory=True,
+                    is_readable=is_readable
+                ))
+            except (PermissionError, OSError):
+                continue
+
+    return items
+