added duplicate check and database

app/utils.py

@@ -0,0 +1,16 @@
+# app/utils.py
+import hashlib
+
+def hash_file(filepath, chunk_size=65536):
+    """
+    Returns the SHA-256 hash of the file at 'filepath'.
+    Reads the file in chunks to handle large files efficiently.
+    """
+    sha256 = hashlib.sha256()
+    with open(filepath, "rb") as f:
+        while True:
+            data = f.read(chunk_size)
+            if not data:
+                break
+            sha256.update(data)
+    return sha256.hexdigest()