FUNDISHA.SITE v31 browser/payment fix

IMPORTANT:
1. This build uses index.php so the payment amount is read server-side from config.php without calling payment_config.php when the account form is submitted.
2. Set SONICPESA_PAYMENT_AMOUNT in config.php (e.g. 200, 300, 400).
3. Keep SONICPESA_API_KEY in config.php only.
4. Upload contents into public_html. Remove/rename any old index.html so index.php is the homepage.
5. PHP and cURL must be enabled.
6. The actual payment request remains server-controlled; frontend cannot choose the amount.
7. Payment success/countdown is still gated by the server SUCCESS response.
8. This build parses API responses as text before JSON parsing so a hosting error returns a readable message instead of Safari's generic “The string did not match the expected pattern.”
