fix: add missing bets table to migration

The bets schema was defined in schema.ts but never created in
startup.ts, causing crash on index creation referencing bets table.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/db/startup.ts

@@ -126,6 +126,23 @@ export function runMigrations() {
     );
   `)
 
+  sqlite.exec(`
+    CREATE TABLE IF NOT EXISTS bets (
+      id TEXT PRIMARY KEY,
+      fight_id TEXT NOT NULL REFERENCES fights(id),
+      bettor_pubkey TEXT NOT NULL,
+      bot_id TEXT NOT NULL REFERENCES bots(id),
+      amount_sats INTEGER NOT NULL,
+      odds_at_placement REAL NOT NULL,
+      cashu_token TEXT NOT NULL,
+      status TEXT NOT NULL DEFAULT 'pending',
+      payout_sats INTEGER,
+      payout_token TEXT,
+      created_at TEXT NOT NULL,
+      settled_at TEXT
+    );
+  `)
+
   sqlite.exec(`
     CREATE TABLE IF NOT EXISTS analytics (
       date TEXT NOT NULL,