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/i18n/en.i18n.json

@@ -553,6 +553,14 @@
     "revokeConfirm": "Stop vouching for this person?",
     "offline": "You're offline — try again when you're connected"
   },
+  "ratings": {
+    "rate": "Rate this person",
+    "edit": "Edit your rating",
+    "commentHint": "How did it go? (optional)",
+    "fromYourCircle": "{n} from people you know",
+    "retract": "Remove your rating",
+    "saved": "Rating saved"
+  },
   "notifications": {
     "newMessageFrom": "New message from {name}"
   },