feat: add profile fields for local users

DB→domain→API→AP→frontend end-to-end. Fields stored as
JSONB, exposed via PATCH /users/me, serialized as AP
PropertyValue attachment. Editor in federation settings,
display on profile card.

thoughts-frontend/lib/api.ts

@@ -1,6 +1,12 @@
 import { cache } from "react";
 import { z } from "zod";
 
+export const ProfileFieldSchema = z.object({
+  name: z.string(),
+  value: z.string(),
+});
+export type ProfileField = z.infer<typeof ProfileFieldSchema>;
+
 export const UserSchema = z.object({
   id: z.string().uuid(),
   username: z.string(),
@@ -9,6 +15,7 @@ export const UserSchema = z.object({
   avatarUrl: z.string().nullable(),
   headerUrl: z.string().nullable(),
   customCss: z.string().nullable(),
+  profileFields: z.array(ProfileFieldSchema).default([]),
   local: z.boolean(),
   isFollowedByViewer: z.boolean(),
   joinedAt: z.coerce.date().nullable(),
@@ -16,12 +23,6 @@ export const UserSchema = z.object({
 
 export const MeSchema = UserSchema;
 
-export const ProfileFieldSchema = z.object({
-  name: z.string(),
-  value: z.string(),
-});
-export type ProfileField = z.infer<typeof ProfileFieldSchema>;
-
 export const RemoteActorSchema = z.object({
   handle: z.string(),
   displayName: z.string().nullable(),
@@ -77,6 +78,7 @@ export const UpdateProfileSchema = z.object({
   displayName: z.string().max(50).optional(),
   bio: z.string().max(4000).optional(),
   customCss: z.string().optional(),
+  profileFields: z.array(ProfileFieldSchema).max(4).optional(),
 });
 
 export const SearchResultsSchema = z.object({