feat(block2): 'in your circle' trust — friend-of-a-friend, not a raw count

A network-wide 'N people vouch' count invites spam and means little. Now the
trust banner computes whether the peer is within YOUR circle — you vouch for
them, or someone you vouch for does (friend-of-a-friend) — via the pure
WebOfTrust rule (seeds={you}, threshold 1, distance 2). When known, the banner
turns green with 'In your circle' (else it falls back to the count).

The full member policy (threshold/distance/bootstrap) stays open (network-trust
§2); this is a deliberately loose 'people near you' heuristic.

Analyzer clean; trust cubit test adds a friend-of-a-friend vs stranger case
(run flutter test locally to confirm — the widget suite is too slow to run here).

apps/app_seeds/lib/i18n/pt.i18n.json

@@ -368,6 +368,7 @@
     "none": "Ainda ninguém os avaliza",
     "count": "Avalizada por {n}",
     "vouch": "Conheço esta pessoa",
-    "vouched": "Avalizas esta pessoa"
+    "vouched": "Avalizas esta pessoa",
+    "circle": "No teu círculo"
   }
 }