fix: use Python script to filter requirements.txt instead of sed

Replace brittle sed patch with a Python script that:
1. Removes Windows/macOS-only packages (pywin32, pyobjc, etc.)
2. Unpins versions to let pip resolve with system packages from apt

Dockerfile

@@ -33,8 +33,26 @@ RUN export SABNZBD_VERSION=3.7.2 PAR2CMDLINE_VERSION=v0.6.14-mt1 && \
     curl -SL -o /tmp/sabnzbd.tar.gz https://github.com/sabnzbd/sabnzbd/releases/download/${SABNZBD_VERSION}/SABnzbd-${SABNZBD_VERSION}-src.tar.gz && \
     tar xzf /tmp/sabnzbd.tar.gz && \
     mv SABnzbd-* sabnzbd && \
-    sed -i 's/==.*//' /sabnzbd/requirements.txt && \
-    sed -i '/pywin32/d' /sabnzbd/requirements.txt && \
+    python3 -c "
+import re
+with open('/sabnzbd/requirements.txt') as f:
+    lines = f.readlines()
+filtered = []
+for line in lines:
+    stripped = line.strip()
+    # Keep comments and blank lines
+    if not stripped or stripped.startswith('#'):
+        filtered.append(line)
+        continue
+    # Remove platform-specific packages (Windows, macOS)
+    if re.search(r'platform_system\s*==\s*[\"\\'](Windows|Darwin)[\"\\']', stripped):
+        continue
+    # Unpin to let pip resolve with system versions
+    line = re.sub(r'(==|>=|<=|!=|~=|<|>)[\d\.\*\+\-a-zA-Z]+', '', line, count=1)
+    filtered.append(line)
+with open('/sabnzbd/requirements.txt', 'w') as f:
+    f.writelines(filtered)
+" && \
     pip3 install -r /sabnzbd/requirements.txt && \
     chown -R sabnzbd: sabnzbd && \
     curl -o /tmp/par2cmdline-mt.tar.gz https://codeload.github.com/jkansanen/par2cmdline-mt/tar.gz/${PAR2CMDLINE_VERSION} && \