Sniff filetype of downloaded media and add extension

Also download in chunks - fixes 2 x TODOs

poetry.lock

@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry 2.0.0 and should not be changed by hand.
+# This file is automatically @generated by Poetry 2.0.1 and should not be changed by hand.
 
 [[package]]
 name = "aiohappyeyeballs"
@@ -889,6 +889,18 @@ future = "*"
 [package.extras]
 dev = ["Sphinx (==2.1.0)", "future (==0.17.1)", "numpy (==1.16.4)", "pytest (==4.6.1)", "pytest-mock (==1.10.4)", "tox (==3.12.1)"]
 
+[[package]]
+name = "filetype"
+version = "1.2.0"
+description = "Infer file type and MIME type of any file/buffer. No external dependencies."
+optional = false
+python-versions = "*"
+groups = ["main"]
+files = [
+    {file = "filetype-1.2.0-py2.py3-none-any.whl", hash = "sha256:7ce71b6880181241cf7ac8697a2f1eb6a8bd9b429f7ad6d27b8db9ba5f1c2d25"},
+    {file = "filetype-1.2.0.tar.gz", hash = "sha256:66b56cd6474bf41d8c54660347d37afcc3f7d1970648de365c102ef77548aadb"},
+]
+
 [[package]]
 name = "flask"
 version = "3.1.0"
@@ -3296,4 +3308,4 @@ test = ["pytest (>=8.1,<9.0)"]
 [metadata]
 lock-version = "2.1"
 python-versions = ">=3.10,<3.13"
-content-hash = "7c7dc6d26e5af1c9bb6e4393b4ac64b155049d20a9f5317baec48c964a2708ac"
+content-hash = "df1bd49271b2682b82da437c2e6ce3842d116aa0fc7769e9ab9958c91a8647b2"