refactor(peer-support): delete provably dead code (Phase 1)

The Skills Exchange + Peer Support feature was replaced by Community
Connections on 2026-04-05, but several files and code paths were left
in place as backward-compat. None are reachable from the live UI:

- usePeerSupport.js composable: not imported anywhere
- PeerSupportBadge.vue: not imported anywhere
- peer-support.vue: stub redirect with no incoming links
- /api/peer-support.get.js: only consumed by usePeerSupport
- /api/members/me/peer-support.patch.js: same
- profile.patch.js offering/lookingFor write branches: profile form
  no longer sends these fields (only writes communityConnections.*)
- PEER_SUPPORT_ENABLED/DISABLED activity types and renderers: only
  written by the deleted peer-support.patch endpoint. The activityText
  formatter has a fallback for unknown types so existing records
  still display ("peer support enabled" with a generic icon).

Tests updated to drop peerSupportUpdateSchema coverage and the
offering/lookingFor passthrough assertion.

schemas.js cleanup deferred — concurrent communityConnections →
communityEcology rename is in flight in the working tree.

app/composables/usePeerSupport.js

@@ -1,16 +0,0 @@
-export const usePeerSupport = () => {
-  const updateSettings = async (settings) => {
-    return await $fetch('/api/members/me/peer-support', {
-      method: 'PATCH',
-      body: settings
-    });
-  };
-
-  const getSupporters = async (topic) => {
-    return await $fetch('/api/peer-support', {
-      query: topic ? { topic } : {}
-    });
-  };
-
-  return { updateSettings, getSupporters };
-};