Koios provider: lovelace fields will change from strings to numbers in Koios v1.5

Koios plans to change how it sends lovelace amounts. Today they come as strings (`"2000000"`). From Koios v1.5.0 they will come as JSON numbers (`2000000`). This is a breaking change on their side, with no date yet:

- the caution note in the [v1.4.2 release](https://github.com/cardano-community/koios-artifacts/releases/tag/v1.4.2)
- cardano-community/koios-artifacts#412
- cardano-community/koios-artifacts#296

**Why it matters for evolution-sdk**

The Koios provider schemas expect strings for these fields. Some examples in `sdk/provider/internal/Koios.ts`:

- protocol parameters: `key_deposit`, `pool_deposit`, `coins_per_utxo_size`, `drep_deposit`, `gov_action_deposit`, `min_utxo_value`, `min_pool_cost`
- UTxOs: `value` and asset `quantity`
- address balance, account `rewards_available`, and tx `fee` / `deposit`

I took today's mainnet `/epoch_params` response and turned those seven fields into numbers. Decoding it with `ProtocolParametersSchema` then fails:

```
gov_action_deposit: NumberFromString — Encoded side transformation failure
```

So once Koios v1.5 is live, `getProtocolParameters()` will fail. So will building a transaction that relies on it. I expect the other calls above to fail the same way.

Accepting numbers is not enough on its own. Some lovelace values are bigger than 2^53, like the stake totals. `JSON.parse` rounds those without any error.

**Possible directions**

- Ask Koios for text directly: adding `::text` in `select` works today and should keep working after v1.5. For example, `?select=epoch_no,key_deposit::text`. Koios suggests this in their release note. I checked on mainnet: with their preview flag `_lovelace_numeric=true`, `active_stake` comes back as a number, and `active_stake::text` turns it back into a string.
- Or read the JSON in a way that keeps big numbers exact.
- Tests with numbers in these fields would catch the change before Koios ships it.

Start in sdk/provider/internal/Koios.ts and trace ProtocolParametersSchema through getProtocolParameters(), then inspect the schemas for UTxOs, balances, rewards, fees, and deposits. Reproduce the failure with numeric lovelace fields, compare the payload-preserving approaches described in the issue, and add tests using numbers in all affected fields. Done means these responses decode without precision loss.

Scritto dal modello di indicizzazione a partire dal testo della issue.