feat(block2): messages inbox + drawer 'Chat' link (was unreachable)

Chat was only reachable via an offer's 'Message' button, and the drawer 'Chat'
sat on 'coming soon' — so messaging/trust were effectively hidden.
- MessageStore keeps a conversation index (the keystore has no key enumeration)
  and exposes conversations() — peers newest-active-first with their last line.
- ChatListScreen: the messages inbox (tap a conversation → /chat/:pubkey).
- Drawer 'Chat' is now a live destination -> /messages (gated like Market).
- i18n en/es/pt. conversations() covered by a plain test (no widget hang).

Analyzer clean.

apps/app_seeds/lib/ui/app_drawer.dart

@@ -49,6 +49,12 @@ class AppDrawer extends StatelessWidget {
             _DrawerItem(
               icon: const Icon(Icons.chat_bubble),
               label: t.menu.chat,
+              onTap: marketEnabled
+                  ? () {
+                      Navigator.of(context).pop();
+                      context.go('/messages');
+                    }
+                  : null,
             ),
             _DrawerItem(
               icon: const Icon(Icons.favorite),

apps/app_seeds/lib/ui/chat_list_screen.dart

@@ -0,0 +1,79 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+import '../i18n/strings.g.dart';
+import '../services/message_store.dart';
+import 'theme.dart';
+
+/// The messages inbox: past conversations, newest first. Tapping one opens the
+/// chat. Reached from the drawer's "Chat" entry.
+class ChatListScreen extends StatefulWidget {
+  const ChatListScreen({required this.store, super.key});
+
+  final MessageStore store;
+
+  @override
+  State<ChatListScreen> createState() => _ChatListScreenState();
+}
+
+class _ChatListScreenState extends State<ChatListScreen> {
+  List<ChatSummary>? _items;
+
+  @override
+  void initState() {
+    super.initState();
+    _load();
+  }
+
+  Future<void> _load() async {
+    final items = await widget.store.conversations();
+    if (mounted) setState(() => _items = items);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final t = context.t;
+    final items = _items;
+    return Scaffold(
+      appBar: AppBar(title: Text(t.chatList.title)),
+      body: items == null
+          ? const Center(child: CircularProgressIndicator())
+          : items.isEmpty
+              ? Center(
+                  child: Padding(
+                    padding: const EdgeInsets.all(32),
+                    child: Text(
+                      t.chatList.empty,
+                      textAlign: TextAlign.center,
+                      style: const TextStyle(color: seedMuted, fontSize: 15),
+                    ),
+                  ),
+                )
+              : ListView.separated(
+                  itemCount: items.length,
+                  separatorBuilder: (_, _) => const Divider(height: 1),
+                  itemBuilder: (context, i) {
+                    final c = items[i];
+                    return ListTile(
+                      leading: const CircleAvatar(
+                        backgroundColor: seedAvatar,
+                        child: Icon(Icons.person, color: seedOnAvatar),
+                      ),
+                      title: Text(_shortId(c.peerPubkey)),
+                      subtitle: Text(
+                        c.lastText,
+                        maxLines: 1,
+                        overflow: TextOverflow.ellipsis,
+                      ),
+                      onTap: () => context.go('/chat/${c.peerPubkey}'),
+                    );
+                  },
+                ),
+    );
+  }
+}
+
+/// A compact, human-ish rendering of a public key until we resolve names.
+String _shortId(String pubkey) => pubkey.length <= 12
+    ? pubkey
+    : '${pubkey.substring(0, 6)}…${pubkey.substring(pubkey.length - 4)}';