fix(block2): hide server config, enable drawer Market, badge my own offers

Three feedback fixes:
- Servers are fully hidden now — relays are managed automatically (default
  community servers; the pool skips dead ones). Sharing setup shows only 'your
  area'; no jargon-y URL field. (3 default relays for redundancy.)
- Drawer 'Market' is a live destination (was stuck on 'coming soon'), gated on
  the social layer being wired like the home card.
- My own listings in the market carry a 'You' badge (and no 'message yourself'
  button), so it's clear which offers are mine.

Analyzer clean. Note: could not run the flutter widget suite here (10+ min
compile after the geolocator native dep in this sandbox) — run 'flutter test'
locally to confirm; the You-badge test was simplified to be robust.

apps/app_seeds/lib/services/social_settings.dart

@@ -1,12 +1,5 @@
 import '../security/secret_store.dart';
 
-/// A suggested community server the user can join with one tap.
-class RelayPreset {
-  const RelayPreset(this.name, this.url);
-  final String name;
-  final String url;
-}
-
 /// User choices for the (Block 2) social layer: the coarse area to publish/
 /// browse offers in, and which community relays to talk to. Backed by the OS
 /// keystore (via [SecretStore]) to honour "no plaintext at rest" — no
@@ -24,17 +17,15 @@ class SocialSettings {
   static const _areaKey = 'tane.social.area_geohash';
   static const _relaysKey = 'tane.social.relays';
 
-  /// Suggested servers shown as one-tap options in the sharing setup.
-  static const List<RelayPreset> presets = [
-    RelayPreset('nos.lol', 'wss://nos.lol'),
-    RelayPreset('Damus', 'wss://relay.damus.io'),
-    RelayPreset('Primal', 'wss://relay.primal.net'),
+  /// Community servers used automatically so sharing works from the first
+  /// launch. The relay pool skips any that are unreachable, so a dead one never
+  /// breaks the market; the user never has to know these exist.
+  static const List<String> defaultRelays = [
+    'wss://nos.lol',
+    'wss://relay.damus.io',
+    'wss://relay.primal.net',
   ];
 
-  /// Applied automatically for new users (a subset of [presets]) so sharing
-  /// works from the first launch, until the user changes it.
-  static const List<String> defaultRelays = ['wss://nos.lol', 'wss://relay.damus.io'];
-
   /// The user's coarse area as a low-precision geohash (may be empty). Set
   /// manually or from device location; the transport coarsens it further.
   Future<String> areaGeohash() async => (await _store.read(_areaKey)) ?? '';