feat(ratings): Wallapop-style ratings in chat and offer detail

- SocialSession grows a ratings transport (fifth interface on the one
  shared channel).
- PeerRatingCubit: count, locale-aware average, and circleCount — how
  many ratings come from your own circle (reuses the ego-centric trust
  rule), the signal that makes strangers' review-stuffing irrelevant.
- Chat: slim rating strip under the trust banner; you can rate only
  someone you've talked with (soft anchor until the signed bilateral
  exchange form lands). Sheet with 5 stars + optional comment,
  pre-filled for editing, with a take-back action.
- Offer detail: author's stars under their name, with 'N from people
  you know' when your circle rated them; nothing shown when unrated.
- i18n ratings.* (en/es/pt/ast); tests for cubit and sheet.

apps/app_seeds/lib/ui/rating_sheet.dart

@@ -0,0 +1,180 @@
+import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
+
+import '../i18n/strings.g.dart';
+import '../state/peer_rating_cubit.dart';
+import 'theme.dart';
+
+/// A compact "★ 4,5 (12)" pill, plus how many ratings come from people you
+/// know — the signal that makes strangers' reviews easy to weigh.
+class RatingStars extends StatelessWidget {
+  const RatingStars({
+    required this.average,
+    required this.count,
+    this.circleCount = 0,
+    super.key,
+  });
+
+  final double average;
+  final int count;
+  final int circleCount;
+
+  @override
+  Widget build(BuildContext context) {
+    final t = context.t;
+    final locale = Localizations.localeOf(context).toString();
+    final avg = NumberFormat('0.#', locale).format(average);
+    return Wrap(
+      crossAxisAlignment: WrapCrossAlignment.center,
+      spacing: 6,
+      children: [
+        const Icon(Icons.star_rounded, size: 18, color: seedGreen),
+        Text(
+          '$avg ($count)',
+          style: const TextStyle(
+            color: seedOnSurface,
+            fontSize: 13,
+            fontWeight: FontWeight.w600,
+          ),
+        ),
+        if (circleCount > 0)
+          Text(
+            t.ratings.fromYourCircle(n: circleCount),
+            style: const TextStyle(color: seedGreen, fontSize: 13),
+          ),
+      ],
+    );
+  }
+}
+
+/// Opens the bottom sheet to leave, edit or take back your rating of the
+/// peer behind [cubit]. Pre-filled when you already rated.
+Future<void> showRatingSheet(BuildContext context, PeerRatingCubit cubit) {
+  return showModalBottomSheet<void>(
+    context: context,
+    isScrollControlled: true,
+    builder: (context) => Padding(
+      padding: EdgeInsets.only(
+        bottom: MediaQuery.of(context).viewInsets.bottom,
+      ),
+      child: _RatingForm(cubit: cubit),
+    ),
+  );
+}
+
+class _RatingForm extends StatefulWidget {
+  const _RatingForm({required this.cubit});
+
+  final PeerRatingCubit cubit;
+
+  @override
+  State<_RatingForm> createState() => _RatingFormState();
+}
+
+class _RatingFormState extends State<_RatingForm> {
+  late int _stars;
+  late final TextEditingController _comment;
+  bool _saving = false;
+
+  @override
+  void initState() {
+    super.initState();
+    final state = widget.cubit.state;
+    _stars = state.myStars ?? 0;
+    _comment = TextEditingController(text: state.myComment);
+  }
+
+  @override
+  void dispose() {
+    _comment.dispose();
+    super.dispose();
+  }
+
+  Future<void> _save() async {
+    final messenger = ScaffoldMessenger.of(context);
+    final navigator = Navigator.of(context);
+    final saved = context.t.ratings.saved;
+    setState(() => _saving = true);
+    await widget.cubit.rate(_stars, comment: _comment.text.trim());
+    navigator.pop();
+    messenger.showSnackBar(SnackBar(content: Text(saved)));
+  }
+
+  Future<void> _retract() async {
+    final navigator = Navigator.of(context);
+    setState(() => _saving = true);
+    await widget.cubit.retract();
+    navigator.pop();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final t = context.t;
+    final iRated = widget.cubit.state.iRated;
+    return Padding(
+      padding: const EdgeInsets.fromLTRB(24, 20, 24, 24),
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text(
+            iRated ? t.ratings.edit : t.ratings.rate,
+            style: const TextStyle(
+              fontSize: 18,
+              fontWeight: FontWeight.w600,
+              color: seedTitle,
+            ),
+          ),
+          const SizedBox(height: 16),
+          Row(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: [
+              for (var s = 1; s <= 5; s++)
+                IconButton(
+                  key: Key('rating.star.$s'),
+                  iconSize: 36,
+                  onPressed:
+                      _saving ? null : () => setState(() => _stars = s),
+                  icon: Icon(
+                    s <= _stars
+                        ? Icons.star_rounded
+                        : Icons.star_outline_rounded,
+                    color: s <= _stars ? seedGreen : seedMuted,
+                  ),
+                ),
+            ],
+          ),
+          const SizedBox(height: 8),
+          TextField(
+            key: const Key('rating.comment'),
+            controller: _comment,
+            enabled: !_saving,
+            maxLength: 280,
+            maxLines: 2,
+            decoration: InputDecoration(
+              hintText: t.ratings.commentHint,
+              border: const OutlineInputBorder(),
+            ),
+          ),
+          const SizedBox(height: 8),
+          Row(
+            children: [
+              if (iRated)
+                TextButton(
+                  key: const Key('rating.retract'),
+                  onPressed: _saving ? null : _retract,
+                  child: Text(t.ratings.retract),
+                ),
+              const Spacer(),
+              FilledButton(
+                key: const Key('rating.save'),
+                onPressed: _saving || _stars == 0 ? null : _save,
+                child: Text(t.common.save),
+              ),
+            ],
+          ),
+        ],
+      ),
+    );
+  }
+}