mealie: reconcile BASE_URL with the domain actually chosen at the Caddy prompt

Confirmed live: install_mealie() pre-computes BASE_URL as
recipes<suffix>.$SITE_DOMAIN before ever asking about Caddy, then
configure_caddy_for_service() separately prompts for a domain — which the
user can freely override (e.g. typing mealie.mydomain.com instead of
accepting the recipes.mydomain.com default). Nothing fed that choice back
into BASE_URL, so it stayed stale. Since BASE_URL is exactly what
_mealie_offer_authelia_oidc() registers as the OIDC redirect URI, this
produced Authelia's "redirect_uri does not match any of the OAuth 2.0
Client's pre-registered redirect_uris" — Caddy and DNS were both correctly
pointed at the new domain, but the client Authelia had on file still said
the old one.

Added CADDY_SERVICE_DOMAIN as a new configure_caddy_for_service() out-param
(lib/common.sh) — the same out-param convention as the existing
CADDY_SERVICE_CONFIGURED/CADDY_SERVICE_MODE, set right after the domain
prompt is accepted. install_mealie() now reconciles BASE_URL against it
immediately after the Caddy call, before the Authelia OIDC step reads
BASE_URL back out of .env. ActualBudget's equivalent OIDC offer asks for
its own domain fresh each time rather than reading a pre-computed BASE_URL,
so it isn't affected by this class of bug and needs no equivalent fix.

Verified the reconciliation logic in isolation against a synthetic .env.

lib/common.sh

@@ -856,6 +856,7 @@ configure_caddy_for_service() {
     # already the only intended way in, instead of leaving both routes open.
     CADDY_SERVICE_CONFIGURED=false
     CADDY_SERVICE_MODE=""
+    CADDY_SERVICE_DOMAIN=""
 
     # Derive the proxy upstream and a port number for display messages.
     # Plain number  → host.docker.internal:PORT  (host-network or legacy
@@ -916,6 +917,15 @@ configure_caddy_for_service() {
     if [ -z "$SERVICE_DOMAIN" ]; then
         echo "  ⚠ No domain provided, skipping Caddy configuration."; return 0
     fi
+    # Set as soon as we know a domain was actually accepted — every path below
+    # this point that returns 0 without configuring Caddy is a genuine failure
+    # (write/reload error), not "no domain chosen", so leaving this set is
+    # correct: the caller can tell CADDY_SERVICE_CONFIGURED apart from whether
+    # a domain was entered at all. Callers that pre-compute their own default
+    # URL/domain before calling this (e.g. services/mealie.sh's BASE_URL) need
+    # this to reconcile against whatever the user actually typed here, which
+    # can differ from that pre-computed default.
+    CADDY_SERVICE_DOMAIN="$SERVICE_DOMAIN"
 
     # Build the site block — upstream differs by mode
     local _BLOCK_UPSTREAM="$_UPSTREAM"