refactor: key instance maps by namespace

[RyukTheCoder]

Summary

Every wallet provider exposes an instances map that the rest of the app uses to reach a chain-specific provider object. Until now that map was keyed by LegacyNetworks (ETH, SOLANA, BTC, …) — a per-chain enum that predates the namespace model. This PR switches all 28 providers to key those maps by namespace (EVM, Solana, UTXO, Tron, Starknet, Ton) from @hub3js/namespaces, and removes the legacy provider implementations that were the last reason for the old keying to exist.

How did you test this change?

• tsc --noEmit passes for every touched package.

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• Implemented a user interface (UI) change, referencing our Figma design to ensure pixel-perfect precision.