feat(web): add persistent beam avatars

frontend/db/migrations/20260807010000_profile_beam_avatars.sql

@@ -0,0 +1,30 @@
+begin;
+
+do $migration$
+begin
+  if to_regclass('identity.users') is not null
+    and to_regclass('public.profiles') is not null then
+    alter table public.profiles
+      add column if not exists avatar_seed uuid not null default gen_random_uuid(),
+      add column if not exists avatar_palette smallint not null
+        default (floor(random() * 8)::smallint),
+      add column if not exists avatar_renderer_version smallint not null default 1;
+
+    alter table public.profiles
+      drop constraint if exists profiles_avatar_palette_check,
+      add constraint profiles_avatar_palette_check
+        check (avatar_palette between 0 and 7),
+      drop constraint if exists profiles_avatar_renderer_version_check,
+      add constraint profiles_avatar_renderer_version_check
+        check (avatar_renderer_version = 1);
+
+    grant update (
+      avatar_seed,
+      avatar_palette,
+      avatar_renderer_version
+    ) on table public.profiles to authenticated;
+  end if;
+end
+$migration$;
+
+commit;