fix(misc): replace generic return 1 with specific exit codes in remaining .func files

Replace 80 generic 'return 1' error returns with specific exit codes
across alpine-tools.func, build.func, core.func, cloud-init.func,
and vm-core.func, matching the EXIT_CODES.md schema.

alpine-tools.func (51 replaced):
- check_for_gh_release, fetch_and_deploy_gh: API/DNS/download errors
- setup_yq, setup_adminer, setup_uv, setup_java, setup_go, setup_composer
- need_tool, download_with_progress

build.func (13 replaced):
- install_ssh_keys_into_ct: file operation errors (252)
- choose_and_set_storage_for_file: parameter/service errors (65/150)
- _find_default_vars, default_var_settings: file not found (252)
- destroy_lxc, resolve_storage_preselect, select_storage: param errors (65)
- validate_storage_space: hardware/space errors (236)

core.func (9 replaced):
- get_header: download failed (250)
- prompt_select: no options (65)
- check_or_create_swap: dd/mkswap/swapon failures (150), invalid size (65)
- get_current_ip, get_lxc_ip: IP detection failed (6)

cloud-init.func (6 replaced):
- setup_cloud_init: invalid IP/gateway format (65)
- configure_cloud_init_interactive: whiptail missing (127)
- get_vm_ip, wait_for_cloud_init: timeout/connection errors (7/150)

vm-core.func (1 replaced):
- get_header: download failed (250)

Boolean returns (validate_*, is_*, prompt_*, 'no update') kept as return 1.

misc/core.func

@@ -858,7 +858,7 @@ get_header() {
   if [ ! -s "$local_header_path" ]; then
     if ! curl -fsSL "$header_url" -o "$local_header_path"; then
       msg_warn "Failed to download header: $header_url"
-      return 1
+      return 250
     fi
   fi
 
@@ -1358,7 +1358,7 @@ prompt_select() {
   if [[ $num_options -eq 0 ]]; then
     msg_warn "prompt_select called with no options"
     echo "" >&2
-    return 1
+    return 65
   fi
 
   # Validate default
@@ -1600,7 +1600,7 @@ check_or_create_swap() {
   swap_size_mb=$(prompt_input "Enter swap size in MB (e.g., 2048 for 2GB):" "2048" 60)
   if ! [[ "$swap_size_mb" =~ ^[0-9]+$ ]]; then
     msg_error "Invalid swap size: '${swap_size_mb}' (must be a number in MB)"
-    return 1
+    return 65
   fi
 
   local swap_file="/swapfile"
@@ -1608,19 +1608,19 @@ check_or_create_swap() {
   msg_info "Creating ${swap_size_mb}MB swap file at $swap_file"
   if ! dd if=/dev/zero of="$swap_file" bs=1M count="$swap_size_mb" status=progress; then
     msg_error "Failed to allocate swap file (dd failed)"
-    return 1
+    return 150
   fi
   if ! chmod 600 "$swap_file"; then
     msg_error "Failed to set permissions on $swap_file"
-    return 1
+    return 150
   fi
   if ! mkswap "$swap_file"; then
     msg_error "Failed to format swap file (mkswap failed)"
-    return 1
+    return 150
   fi
   if ! swapon "$swap_file"; then
     msg_error "Failed to activate swap (swapon failed)"
-    return 1
+    return 150
   fi
   msg_ok "Swap file created and activated successfully"
 }
@@ -1699,13 +1699,13 @@ function get_lxc_ip() {
         fi
       done
 
-      return 1
+      return 6
     }
 
     LOCAL_IP="$(get_current_ip || true)"
     if [[ -z "$LOCAL_IP" ]]; then
       msg_error "Could not determine LOCAL_IP (checked: eth0, hostname -I, ip route, IPv6 targets)"
-      return 1
+      return 6
     fi
   fi