fix(api): don't undo domain verification on DNS re-check, fix theme lookup crash

- domains.ts: a proxied Cloudflare custom hostname's real CNAME target
  is never visible to a plain DNS lookup, so a re-verify always fails
  and was silently downgrading already-verified domains back to
  pending. Only a first-time check can now land on pending.
- restaurants.ts: PUT /restaurants/:id/theme referenced an undeclared
  themeData variable (pre-existing tsc error on main, not introduced
  here) — added the missing themes-by-key lookup it depended on.

apps/api/src/routes/domains.ts

@@ -179,7 +179,12 @@ export const domainsRoutes: FastifyPluginAsync = async (app) => {
       });
     }
 
-    // If not verified, set/keep status as pending or failed
+    // A DNS CNAME lookup structurally cannot see the real target once the
+    // record is proxied (Cloudflare hides it behind its own edge IPs) — so a
+    // failed re-check here is inconclusive, not proof the domain broke.
+    // Never downgrade a domain that was already verified; only a first-time
+    // check is allowed to land on "pending".
+    if (domain.status !== "verified") {
       await supabase
         .from("domains")
         .update({
@@ -187,10 +192,11 @@ export const domainsRoutes: FastifyPluginAsync = async (app) => {
           verified_at: null,
         })
         .eq("id", domainId);
+    }
 
     return reply.send({
-      verified: false,
+      verified: domain.status === "verified",
-      domain: { ...domain, status: "pending", verified_at: null },
+      domain: domain.status === "verified" ? domain : { ...domain, status: "pending", verified_at: null },
       message: `Doğrulanamadı: ${dnsErrorDetails}\n\nLütfen alan adı yönetim panelinizden (Cloudflare, GoDaddy, Natro vb.) ${domain.hostname} için CNAME kaydını ${expectedTarget} adresine yönlendirin.`,
     });
   });

apps/api/src/routes/restaurants.ts

@@ -168,6 +168,8 @@ export const restaurantsRoutes: FastifyPluginAsync = async (app) => {
       classic: "Classic Bistro",
     };
 
+    const { data: themeData } = await supabase.from("themes").select("id").eq("key", themeKey).maybeSingle();
+
     let themeId = themeData?.id;
     if (!themeId) {
       const { data: newTheme } = await supabase