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>

db.js

@@ -64,6 +64,12 @@ async function bootstrap() {
     created BIGINT NOT NULL,
     INDEX (owner_email), INDEX (type, status), INDEX (member_id)
   ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
+  await q(`CREATE TABLE IF NOT EXISTS earned_credits (
+    email VARCHAR(190) PRIMARY KEY,
+    balance INT NOT NULL DEFAULT 0,
+    granted_welcome TINYINT NOT NULL DEFAULT 0,
+    updated BIGINT NOT NULL
+  ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
   await q(`CREATE TABLE IF NOT EXISTS burns (
     id VARCHAR(32) PRIMARY KEY,
     member_id INT NOT NULL,