Fix: remove debug echo from post_to_api, fix dev_index arithmetic in GPU passthrough (set -e compatible)

misc/api.func

@@ -151,8 +151,6 @@ explain_exit_code() {
 # ------------------------------------------------------------------------------
 post_to_api() {
 
-  echo "post_to_api"
-
   if ! command -v curl &>/dev/null; then
     return
   fi

misc/build.func

@@ -2585,7 +2585,7 @@ EOF
       for dev in "${devices[@]}"; do
         # Add to config using pct set (will be visible in GUI)
         echo "dev${dev_index}: ${dev},gid=44" >>"$LXC_CONFIG"
-        ((dev_index++))
+        dev_index=$((dev_index + 1))
       done
 
       export GPU_TYPE="$selected_gpu"
@@ -2602,7 +2602,7 @@ EOF
       local dev_index=0
       for dev in "${NVIDIA_DEVICES[@]}"; do
         echo "dev${dev_index}: ${dev},gid=44" >>"$LXC_CONFIG"
-        ((dev_index++))
+        dev_index=$((dev_index + 1))
       done
 
       export GPU_TYPE="NVIDIA"