feat(block2): default relays + pick-from-list servers (works out of the box)

Feedback: the blank 'web address' field was unusable — nobody knows what to put,
so the market never worked at first launch.
- SocialSettings ships default public relays (nos.lol, relay.damus.io), applied
  automatically for new users so the market works day one. An explicitly empty
  choice still turns the network off (privacy). Exposure is minimal: offers are
  opt-in and carry only a coarse geohash.
- Sharing setup now shows the servers as a short PICK-LIST (checkboxes, pre-
  selected) instead of a blank field; a community's own server goes under a small
  'add another' escape hatch. Intro reworded — no need to know a community.
- Tests updated (defaults) and pinned offline (setRelayUrls([])) so widget tests
  don't hit the network. 22 green, analyzer clean.

apps/app_seeds/lib/i18n/en.i18n.json

@@ -344,12 +344,12 @@
     "near": "Near you",
     "contact": "Message",
     "configTitle": "Sharing setup",
-    "setupIntro": "Sharing with people nearby is optional. To turn it on, set your rough area and join a community you trust — a seed network or collective that runs a shared meeting point for passing messages. No company in the middle.",
+    "setupIntro": "Sharing with people nearby is optional. Just set your rough area — you're already connected to shared community servers so people can find what you offer, with no company in the middle. You can change the servers below.",
     "areaLabel": "Your area",
     "areaHelp": "Kept rough on purpose — your zone, never an exact spot.",
-    "serversAdvanced": "Join a community (advanced)",
-    "serversHelp": "Your seed network or collective gives you a web address to connect to. Paste one per line. Leave empty if you don't have one yet.",
-    "serversLabel": "Web address",
+    "serversLabel": "Community servers",
+    "serversHelp": "Pick one or more shared servers. Anyone can use them — or add your own community's below.",
+    "serversAdvanced": "Add another server",
     "save": "Save",
     "saved": "Saved",
     "wanted": "Wanted",