Refactor for GRAM (ex TON) integration

- Updated imports and references from TON to GRAM across multiple modules.
- Renamed functions and variables to reflect the change from TON to GRAM.
- Adjusted validation checks for top-up and recharge amounts to use GRAM limits.
- Modified error messages and exceptions to indicate GRAM instead of TON.
- Updated tests to ensure they reflect the new GRAM terminology and functionality.
- Introduced new constants for GRAM-related configurations.

CHANGELOG.md

@@ -24,6 +24,34 @@ and this project uses [Calendar Versioning](https://calver.org/) (`YYYY.MINOR.MI
 - Updated `DEVICE_INFO` fingerprint: Tonkeeper `appVersion` -> `26.05.0`.
 - Updated client docstrings and purchase examples to document all supported payment methods.
 
+### Renamed — TON -> GRAM (ex TON)
+
+The TON blockchain has been rebranded to **GRAM (ex TON)**. All identifiers, messages, and documentation have been updated accordingly.
+
+**Public API**
+
+- `FragmentClient.topup_ton()` → `topup_gram()`
+- `PaymentMethod.TON` → `PaymentMethod.GRAM`
+- `PaymentMethod.USDT_TON` → `PaymentMethod.USDT_GRAM`
+- `WalletInfo.ton_balance` → `WalletInfo.gram_balance`
+
+**Constants**
+
+- `TON_TOPUP_MIN` / `TON_TOPUP_MAX` → `GRAM_TOPUP_MIN` / `GRAM_TOPUP_MAX`
+- `MIN_TON_BALANCE` → `MIN_GRAM_BALANCE`
+- `USDT_TON_MASTER_ADDRESS` → `USDT_GRAM_MASTER_ADDRESS`
+
+**Exceptions**
+
+- `ConfigurationError.INVALID_TON_AMOUNT` → `INVALID_GRAM_AMOUNT`
+- `WalletError.LOW_TON_BALANCE` → `LOW_GRAM_BALANCE`
+- `WalletError.TON_BALANCE_CHECK_FAILED` → `GRAM_BALANCE_CHECK_FAILED`
+
+**Internals**
+
+- `pyfragment/core/constants/ton.py` → `gram.py`
+- `check_ton_payment_balance()` → `check_gram_payment_balance()`
+
 ---
 
 ## [2026.3.1] — 2026-05-29
@@ -239,6 +267,8 @@ and this project uses [Calendar Versioning](https://calver.org/) (`YYYY.MINOR.MI
 - `py.typed` marker — full PEP 561 typing support for type-checkers
 - `__repr__` on all result types for readable debug output
 
+[2026.3.2]: https://github.com/bohd4nx/pyfragment/releases/tag/v2026.3.2
+[2026.3.1]: https://github.com/bohd4nx/pyfragment/releases/tag/v2026.3.1
 [2026.3.0]: https://github.com/bohd4nx/pyfragment/releases/tag/v2026.3.0
 [2026.2.3]: https://github.com/bohd4nx/pyfragment/releases/tag/v2026.2.3
 [2026.2.2]: https://github.com/bohd4nx/pyfragment/releases/tag/v2026.2.2