docs: correct TON gasless configuration

[ihsraham]

Summary

• Correct TON Center examples to use the v2 JSON-RPC endpoint required by @ton/ton's TonClient.
• Correct TON Gasless tonApiClient.url examples to use the TON API base URL and document why /v2 must not be included.
• Clarify paymasterToken shape, quoteTransfer() fee-only return value, unsupported native TON sends in the gasless module, on-chain initialization prerequisites, and default derivation path mismatch between TON modules.
• Update the WDK TON reference notes to match the documented behavior.

Root cause

The docs mixed TON Center v3 REST-style URLs with @ton/ton JSON-RPC client usage, and TON API base URLs with paths that the generated TON API client already appends internally. The gasless docs also implied broader native TON transaction support than the module provides.

Validation

• git diff --check upstream/develop..HEAD
• Searched for stale TON Gasless /api/v3, tonapi.io/v2, raw-string paymasterToken, and quote hash examples. Remaining matches are unrelated swap docs or the non-gasless TON module.
• No repo-root package.json, so no local docs build command was available.