In-app notification inbox, consolidate /profile into /me, theme realign

In-app notification center (Phase 5, migration 051):
- notifications.read_at + partial unread index. /me Notifications is now
  an inbox: unread styling, click to expand the message + mark read,
  "mark all as read", unread count. markNotificationsRead is a service-
  client write scoped to the caller's own member_id. Always-on channel:
  email-muted ('skipped') notifications still appear in-app.

Consolidate /profile into /me:
- Delete app/(app)/profile/*; /me is the single member page. Port the
  conflict-of-interest privileged-role nudge + last-disclosed date into
  /me's profile editor. Remove the "My profile" sidebar + command-palette
  entries; rename the /me nav label to "My membership". Repoint the
  recruitment empty-state link to /me.

Theme realign:
- Revert the rounded-lg cards introduced in the prior /me visual pass to
  rounded (the app norm, matching the former /profile). Route /me section
  headers through the SectionTitle primitive.

Regression guard:
- integration/auth-embed.test.ts runs the auth layout's
  space_members.select('*, spaces(*)') embed through PostgREST and fails
  on PGRST201, so a future junction table cannot silently break auth again.

app/(app)/me/notification-prefs.tsx

@@ -29,7 +29,7 @@ export function NotificationPrefs({ initial }: { initial: PrefMap }) {
   }
 
   return (
-    <ul className="divide-y rounded-lg border border-border">
+    <ul className="divide-y rounded border border-border">
       {CATEGORY_META.map(meta => {
         const enabled = prefs[meta.category] ?? true
         return (