Fix QuickXorHash: XOR længde ind i de sidste 64 bit (bits 96-159)

- Korrigerer finaliseringslogikken så filstørrelsen XOR'es ind i de mest betydende 64 bit af 160-bit staten
- Tidligere version XOR'ede i de mindst betydende bit, hvilket gav forkerte hashes
- Dette matcher nu præcis Microsofts specifikation og fjerner falske hash-mismatches

download_sharepoint.py

@@ -80,8 +80,8 @@ def safe_get(url, headers, stream=False, timeout=60, params=None):
 # --- Punkt 4: Integrity Validation (QuickXorHash) ---
 def quickxorhash(file_path):
     """Compute Microsoft QuickXorHash for a file. Returns base64-encoded string.
-    Follows the official Microsoft/Rclone implementation: 
-    160-bit circular XOR with a final length XOR."""
+    Follows the official Microsoft implementation: 160-bit circular XOR
+    with the file length XORed into the LAST 64 bits."""
     h = 0
     length = 0
     mask = (1 << 160) - 1
@@ -93,16 +93,14 @@ def quickxorhash(file_path):
                 break
             for b in chunk:
                 shift = (length * 11) % 160
-                # Circular shift left: the byte is XORed into the 160-bit state
-                # at a position that rotates 11 bits for every byte.
                 shifted = b << shift
                 wrapped = (shifted & mask) | (shifted >> 160)
                 h ^= wrapped
                 length += 1
     
-    # Finalize: XOR the 64-bit length into the 160-bit state.
-    # This affects the first 8 bytes of the little-endian representation.
-    h ^= length
+    # Finalize: XOR the 64-bit length into the LAST 64 bits of the 160-bit state.
+    # Bits 96 to 159.
+    h ^= (length << (160 - 64))
     
     # Convert to 20 bytes (160 bits) in little-endian format
     result = h.to_bytes(20, byteorder='little')