Welcome credits (spec 8b earned pool v1) + official rehearsal rate card

Every account gets welcomeCredits (25, rate-card configurable) via an
idempotent lazy grant on dashboard load, so existing members receive theirs
retroactively. earned_credits table with JSON fallback; Overview stat shows
the purchased/welcome split. Chatbot facts and canned answers synced;
homepage free-membership list mentions the welcome batch. Rate card
promoted from placeholder to decided and persisted in the volume.
Spending integration for the earned pool is the next engine build.
Assets v=20260905b.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server.js

@@ -316,7 +316,8 @@ const server = http.createServer(async (req, res) => {
       const out = { memberId, email: s.email || (acct && acct.email) || null,
         address: s.address || (acct && acct.address) || null,
         refCode: (acct && acct.code) || null, credits: 0, buyerCount: 0,
-        earnedWei: '0', earnCount: 0, referrals: [] };
+        earnedWei: '0', earnCount: 0, referrals: [], welcomeCredits: 0 };
+      if (out.email) out.welcomeCredits = await ads.grantWelcome(out.email); // idempotent lazy grant
       if (memberId) {
         try {
           const mm = await chain.member(memberId);