ci: update test job to use matrix strategy for multiple Python versions and switch to conda setup

fix: specify type for headers parameter in execute_transaction_request
fix: specify type for transaction_data parameter in process_transaction
deps: update tonutils dependency version to 2.0.5

pyfragment/utils/http.py

@@ -114,7 +114,7 @@ async def fragment_request(
 
 async def execute_transaction_request(
     session: httpx.AsyncClient,
-    headers: dict,
+    headers: dict[str, str],
     tx_data: dict[str, Any],
     fragment_hash: str,
 ) -> dict[str, Any]:

pyfragment/utils/wallet.py

@@ -16,7 +16,7 @@ if TYPE_CHECKING:
     from pyfragment.client import FragmentClient
 
 
-async def process_transaction(client: "FragmentClient", transaction_data: dict) -> str:
+async def process_transaction(client: "FragmentClient", transaction_data: dict[str, Any]) -> str:
     """Sign and broadcast a Fragment transaction to the TON network.
 
     Validates the payload structure, checks the wallet balance, decodes the