fix: Use current sid/testing ISO instead of 13.0.0

Updates build-iso.sh:
- Removes assumption of 13.0.0 release availability
- Uses current sid ISO (trixie is still testing)
- More reliable URL path
- Simpler download logic

💘 Generated with Crush

Assisted-by: Gemini 2.5 Flash via Crush <crush@charm.land>

build-iso.sh

@@ -32,16 +32,15 @@ docker run --rm \
         apt-get install -y -qq wget xorriso
 
         echo ""
-        echo "Downloading Debian 13 Trixie Netboot ISO..."
+        echo "Downloading Debian Netboot ISO..."
         cd /build/iso-tmp
 
-        # Download Debian 13 (trixie) released ISO
+        # Download current testing/sid ISO (trixie is still testing)
         wget -q --show-progress \
-            -O debian-trixie-amd64-netinst.iso \
-            https://cdimage.debian.org/debian-cd/13.0.0/amd64/iso-cd/debian-13.0.0-amd64-netinst.iso || \
-        # Fallback to testing if 13.0.0 not available
+            -O debian-amd64-netinst.iso \
+            https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-sid-amd64-netinst.iso || \
         wget -q --show-progress \
-            -O debian-trixie-amd64-netinst.iso \
+            -O debian-amd64-netinst.iso \
             https://cdimage.debian.org/debian-cd/testing/amd64/iso-cd/debian-testing-amd64-netinst.iso
 
         echo ""