Implement shared Caddy setup with initializing and unavailable pages for various apps

- Refactor domain scripts for Ghost, Gitea, Jellyfin, Metabase, n8n, NocoDB, Open WebUI, OpenClaw, PicoClaw, Plausible, Signoz, Uptime Kuma, and Vaultwarden to utilize a common Caddy setup script.
- Introduce `caddy-setup.sh` for managing Caddy configurations and handling app initialization states.
- Create `initializing.html` and `unavailable.html` pages to provide user feedback during app deployment and downtime.
- Update domain handling logic to ensure seamless transitions between initializing and operational states.
- Enhance user experience by providing visual indicators for app status during setup and maintenance.

_common/caddy-setup.sh

@@ -0,0 +1,130 @@
+#!/bin/bash
+#
+# Shared Caddy setup with initializing/unavailable pages.
+#
+# Usage in domain.sh:
+#   source /var/excloud/scripts/caddy-setup.sh
+#   setup_initializing_page "$DOMAIN" "$APP_NAME" "$APP_DIR/$APP_NAME"
+#   ... start containers ...
+#   wait_and_switch_to_proxy "$DOMAIN" "$APP_UPSTREAM_PORT" "$APP_DIR/$APP_NAME" &
+#
+# For apps with custom Caddyfile (e.g. signoz with multi-route), use:
+#   write_loading_pages "$APP_NAME" "$APP_DIR/$APP_NAME"
+#   setup_initializing_page "$DOMAIN" "$APP_NAME" "$APP_DIR/$APP_NAME"
+#   ... start containers ...
+#   wait_and_switch_to_proxy "$DOMAIN" "$APP_UPSTREAM_PORT" "$APP_DIR/$APP_NAME" "$CUSTOM_CADDYFILE_CONTENT" &
+
+SCRIPT_DIR_CADDY="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+write_loading_pages() {
+    local app_name="$1"
+    local app_dir="$2"
+
+    local display_name
+    display_name="$(echo "$app_name" | sed 's/-/ /g' | awk '{for(i=1;i<=NF;i++) $i=toupper(substr($i,1,1)) substr($i,2)}1')"
+
+    mkdir -p "${app_dir}/.excloud"
+
+    cp "${SCRIPT_DIR_CADDY}/initializing.html" "${app_dir}/.excloud/initializing.html"
+    cp "${SCRIPT_DIR_CADDY}/unavailable.html" "${app_dir}/.excloud/unavailable.html"
+
+    sed -i "s/APP_DISPLAY_NAME/${display_name}/g" "${app_dir}/.excloud/initializing.html"
+    sed -i "s/APP_DISPLAY_NAME/${display_name}/g" "${app_dir}/.excloud/unavailable.html"
+}
+
+# Phase 1: Serve the initializing page immediately via Caddy file_server.
+setup_initializing_page() {
+    local domain="$1"
+    local app_name="$2"
+    local app_dir="$3"
+
+    write_loading_pages "$app_name" "$app_dir"
+
+    cat > /etc/caddy/Caddyfile <<EOF
+https://${domain} {
+        root * ${app_dir}/.excloud
+        rewrite * /initializing.html
+        file_server
+}
+EOF
+
+    systemctl enable caddy
+    systemctl reload caddy
+    echo "Caddy serving initializing page for ${app_name}"
+}
+
+# Phase 2 (runs in background): Poll the upstream port, then switch Caddy to reverse_proxy.
+# Accepts an optional 4th argument with custom Caddyfile content for apps like signoz.
+wait_and_switch_to_proxy() {
+    local domain="$1"
+    local port="$2"
+    local app_dir="$3"
+    local custom_caddyfile="${4:-}"
+
+    # Wait for the app to respond (up to 20 minutes)
+    local start_time
+    start_time="$(date +%s)"
+    while ! curl -fsS -o /dev/null "http://127.0.0.1:${port}" 2>/dev/null; do
+        if [ $(( $(date +%s) - start_time )) -ge 1200 ]; then
+            echo "App did not become ready within 20 minutes" >&2
+            break
+        fi
+        sleep 5
+    done
+
+    # Switch to reverse proxy with handle_errors for unavailable page
+    if [ -n "$custom_caddyfile" ]; then
+        echo "$custom_caddyfile" > /etc/caddy/Caddyfile
+    else
+        cat > /etc/caddy/Caddyfile <<EOF
+https://${domain} {
+        reverse_proxy 127.0.0.1:${port}
+        handle_errors {
+                root * ${app_dir}/.excloud
+                rewrite * /unavailable.html
+                file_server
+        }
+}
+EOF
+    fi
+
+    touch "${app_dir}/.excloud/.ready"
+    systemctl reload caddy
+    echo "App is ready — Caddy switched to reverse proxy"
+}
+
+# Quick domain swap for an already-running app. Skips the initializing page
+# and background watcher — just updates the Caddyfile and reloads.
+# Accepts an optional 4th argument with custom Caddyfile content.
+switch_domain() {
+    local domain="$1"
+    local port="$2"
+    local app_dir="$3"
+    local custom_caddyfile="${4:-}"
+
+    write_loading_pages "$(basename "$app_dir")" "$app_dir"
+
+    if [ -n "$custom_caddyfile" ]; then
+        echo "$custom_caddyfile" > /etc/caddy/Caddyfile
+    else
+        cat > /etc/caddy/Caddyfile <<EOF
+https://${domain} {
+        reverse_proxy 127.0.0.1:${port}
+        handle_errors {
+                root * ${app_dir}/.excloud
+                rewrite * /unavailable.html
+                file_server
+        }
+}
+EOF
+    fi
+
+    systemctl reload caddy
+    echo "Domain switched to ${domain}"
+}
+
+# Returns 0 if the app has completed first-time setup, 1 otherwise.
+is_app_ready() {
+    local app_dir="$1"
+    [ -f "${app_dir}/.excloud/.ready" ]
+}