core: add IPv6 fallback support to get_current_ip functions | add check for SSH_KEYS_FILE in user_defaults (#11067)

* fix(core): add IPv6 fallback support to get_current_ip functions

Fixes IP detection in IPv6-only environments by adding fallback:
- Try IPv4 first (existing behavior)
- Fall back to IPv6 via interface lookup (eth0 scope global)
- Fall back to IPv6 routing with Google/Cloudflare DNS targets

Closes #issue-ipv6-only-environment

* fix(build): use SSH_AUTHORIZED_KEY from user defaults when no SSH_KEYS_FILE exists

When using 'User Defaults' with var_ssh_authorized_key set in default.vars,
the SSH key was not being installed because install_ssh_keys_into_ct() only
checked for SSH_KEYS_FILE (which is only created in Advanced Settings).

Now the function also checks SSH_AUTHORIZED_KEY and creates a temporary
SSH_KEYS_FILE if needed.

Fixes #11062

misc/tools.func

@@ -3548,10 +3548,11 @@ IP_FILE="/run/local-ip.env"
 mkdir -p "$(dirname "$IP_FILE")"
 
 get_current_ip() {
-    local targets=("8.8.8.8" "1.1.1.1" "192.168.1.1" "10.0.0.1" "172.16.0.1" "default")
     local ip
 
-    for target in "${targets[@]}"; do
+    # Try IPv4 targets first
+    local ipv4_targets=("8.8.8.8" "1.1.1.1" "192.168.1.1" "10.0.0.1" "172.16.0.1" "default")
+    for target in "${ipv4_targets[@]}"; do
         if [[ "$target" == "default" ]]; then
             ip=$(ip route get 1 2>/dev/null | awk '{for(i=1;i<=NF;i++) if ($i=="src") print $(i+1)}')
         else
@@ -3563,6 +3564,23 @@ get_current_ip() {
         fi
     done
 
+    # IPv6 fallback: Try direct interface lookup for eth0
+    ip=$(ip -6 addr show eth0 scope global 2>/dev/null | awk '/inet6 / {print $2}' | cut -d/ -f1 | head -n1)
+    if [[ -n "$ip" && "$ip" =~ : ]]; then
+        echo "$ip"
+        return 0
+    fi
+
+    # IPv6 fallback: Use routing table with IPv6 targets (Google DNS, Cloudflare DNS)
+    local ipv6_targets=("2001:4860:4860::8888" "2606:4700:4700::1111")
+    for target in "${ipv6_targets[@]}"; do
+        ip=$(ip -6 route get "$target" 2>/dev/null | awk '{for(i=1;i<=NF;i++) if ($i=="src") print $(i+1)}')
+        if [[ -n "$ip" && "$ip" =~ : ]]; then
+            echo "$ip"
+            return 0
+        fi
+    done
+
     return 1
 }