feat: implement proper Debian Package Registry setup

Replace Generic Package Registry with proper Debian Package Registry using
correct API endpoint and authentication. Update workflow to use POST method
with form data and proper Bearer token authentication. Update README with
professional apt repository setup including GPG key verification and proper
installation instructions following Forgejo documentation.

.forgejo/workflows/build-libostree-backport.yml

@@ -138,27 +138,21 @@ jobs:
           apt-get update -y
           apt-get install -y curl
 
-      - name: Upload to Generic Package Registry
+      - name: Upload to Debian Package Registry
         run: |
-          # Upload each .deb package to Forgejo's Generic Package Registry
+          # Upload each .deb package to Forgejo's Debian Package Registry
           for deb_file in release-assets/*.deb; do
             if [ -f "$deb_file" ]; then
-              echo "Uploading $deb_file to Generic Package Registry..."
+              echo "Uploading $deb_file to Debian Package Registry..."
               
-              # Extract filename for the package
-              filename=$(basename "$deb_file")
-              package_name=$(echo "$filename" | cut -d'_' -f1)
-              version=$(echo "$filename" | cut -d'_' -f2 | cut -d'~' -f1)
-              
-              echo "Package: $package_name"
-              echo "Version: $version"
-              echo "File: $filename"
-              
-              # Upload to Forgejo's Generic Package Registry
-              # PUT https://forgejo.example.com/api/packages/{owner}/generic/{package_name}/{package_version}/{file_name}
-              curl --user "robojerk:${{ secrets.ACCESS_TOKEN }}" \
-                   --upload-file "$deb_file" \
-                   "https://git.raines.xyz/api/packages/robojerk/generic/$package_name/$version/$filename"
+              # Upload to Forgejo's Debian Package Registry using the correct API
+              # POST /api/v1/repos/{owner}/{repo}/packages/debian
+              curl -X POST \
+                   -H "Authorization: Bearer ${{ secrets.ACCESS_TOKEN }}" \
+                   -F "file=@$deb_file" \
+                   -F "distribution=noble" \
+                   -F "component=main" \
+                   "https://git.raines.xyz/api/v1/repos/robojerk/libostree-dev/packages/debian"
               
               echo "Upload completed for $deb_file"
             fi