feat: Add Advoware History and Watcher services for document synchronization

- Implement AdvowareHistoryService for fetching and creating history entries.
- Implement AdvowareWatcherService for file operations including listing, downloading, and uploading with Blake3 hash verification.
- Introduce Blake3 utility functions for hash computation and verification.
- Create document sync cron step to poll Redis for pending Aktennummern and emit sync events.
- Develop document sync event handler to manage 3-way merge synchronization for Akten, including metadata updates and error handling.

services/blake3_utils.py

@@ -0,0 +1,47 @@
+"""
+Blake3 Hash Utilities
+
+Provides Blake3 hash computation for file integrity verification.
+"""
+
+from typing import Union
+
+
+def compute_blake3(content: bytes) -> str:
+    """
+    Compute Blake3 hash of content.
+    
+    Args:
+        content: File bytes
+    
+    Returns:
+        Hex string (lowercase)
+        
+    Raises:
+        ImportError: If blake3 module not installed
+    """
+    try:
+        import blake3
+    except ImportError:
+        raise ImportError(
+            "blake3 module not installed. Install with: pip install blake3"
+        )
+    
+    hasher = blake3.blake3()
+    hasher.update(content)
+    return hasher.hexdigest()
+
+
+def verify_blake3(content: bytes, expected_hash: str) -> bool:
+    """
+    Verify Blake3 hash of content.
+    
+    Args:
+        content: File bytes
+        expected_hash: Expected hex hash (lowercase)
+    
+    Returns:
+        True if hash matches, False otherwise
+    """
+    computed = compute_blake3(content)
+    return computed.lower() == expected_hash.lower()