refactor: rename points earn endpoint to /points/earn for clarity

Use /points/earn and /points/redeem consistently for explicit intent.

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

app/modules/loyalty/static/store/js/loyalty-terminal.js

@@ -220,7 +220,7 @@ function storeLoyaltyTerminal() {
         async earnPoints() {
             loyaltyTerminalLog.info('Earning points...', { amount: this.earnAmount });
 
-            const response = await apiClient.post('/store/loyalty/points', {
+            const response = await apiClient.post('/store/loyalty/points/earn', {
                 card_id: this.selectedCard.id,
                 purchase_amount_cents: Math.round(this.earnAmount * 100),
                 staff_pin: this.pinDigits