fix(themes): use checkValidity for live price gating

[Ahmed-S-Abduallah]

🔍 Problem

After #996, live product price sometimes does not update when selecting product options. The gate that iterates form.elements and reads el.validity.valid can fail on some controls (e.g. fieldset) and block the price request entirely — matching SP-22004 (“no request on option change”).

https://sallaops.youtrack.cloud/issue/SP-22004

✅ Changes

• 🛠️ Replace the manual validity.valid loop with form.checkValidity()
• 🐛 Keep the same required-fields gate without reportValidity() focus/scroll side effects
• 📦 Rebuild public/product.js

🧪 Testing

🔗 Test link: https://ofqextra.sa/WlvYKGg

• Change priced product options and confirm a price request is sent
• Confirm live price updates when constraints are satisfied
• Confirm no scroll/focus jump while required fields are still empty
• Confirm add-to-cart required validation still works

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 0 duplication

Metric	Results
Duplication	✅ 0 (≤ 2 duplication)

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_{TIP This summary will be updated as you push new changes.}