fix(admin): invite magic link is absolute, not relative

The Create Invitation flow rendered "/invite?t=…" instead of
"https://host/invite?t=…" because the origin was gated on an unset
PUBLIC_ORIGIN env var.

Solution: OpContext now carries `origin` (always set by the route
handler from Astro.url.origin), and invitations.ts builds the magic
link from it. No env vars required.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/admin/resource-types.ts

@@ -221,6 +221,9 @@ export interface FormConfig {
 // ── Op context — passed to CRUD ops and actions ─────────────────────────────
 export interface OpContext {
   user: { id: number; role: string };
+  /** Request origin (e.g. "https://bifrost.fenja.ai") — used to build absolute
+   *  URLs in ActionResults like invite links. Always set by the route handler. */
+  origin: string;
   /**
    * Raw POST FormData — opt-in escape hatch for resources whose form has
    * embedded sub-forms (e.g. the pulse fieldset inside dispatches). Most

src/admin/resources/invitations.ts

@@ -166,11 +166,11 @@ export const invitationsResource: Resource<InviteRow> = {
 
       // Surface the one-shot magic link via the result mechanism — the route
       // handler propagates it as ?invite_url= and the panel renders a copy
-      // block on the next page load.
-      const origin = process.env.PUBLIC_ORIGIN ?? '';
+      // block on the next page load. ctx.origin comes from Astro.url.origin
+      // so the link is always absolute and clickable.
       ctx.result = {
         kind: 'invite-link',
-        url: `${origin}/invite?t=${token}`,
+        url: `${ctx.origin}/invite?t=${token}`,
       };
       return id;
     },

src/pages/admin/[resource].astro

@@ -38,7 +38,10 @@ if (!resource) {
 }
 
 const resourceBase = `/admin/${resource.key}`;
-const opCtx: OpContext = { user: { id: user.id, role: user.role } };
+const opCtx: OpContext = {
+  user: { id: user.id, role: user.role },
+  origin: Astro.url.origin,
+};
 
 // ── Form-data → typed record (driven by the field configs) ────────────────
 function parseFormData(