feat: add GET /v0/blockInfo/{blockHash} endpoint

[lysyi3m]

Purpose

Adds a new GET /v0/blockInfo/{blockHash} endpoint that returns metadata for a block identified by its hash.

Motivation

Following up on #169 — wallet clients that need to query chain history currently require a direct gRPC connection to the node. A blockInfo endpoint through the proxy allows fetching block metadata (height, baker, transaction count, timestamps, finalization status) via REST, without a gRPC client.

Changes

• src/Proxy.hs: New route /v0/blockInfo/#Text BlockInfoR GET and handler (~15 lines)
• src/Internationalization/Base.hs: New EMMalformedBlockHash error constructor
• src/Internationalization/En.hs: English translation for the new error
• ChangeLog.md: Entry under [unreleased]
• README.md: Endpoint listed + full response format documentation

Implementation

Parses the block hash from the path using readMaybe, calls getBlockInfo (Given blockHash), and returns the result directly as JSON. The BlockInfo type already has a ToJSON instance via deriveJSON, so no manual field mapping is needed. Returns 404 if the block hash is not found, 400 if the hash is malformed.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

By submitting the contribution I accept the terms and conditions of the
Contributor License Agreement v1.0

• link: https://developers.concordium.com/CLAs/Contributor-License-Agreement-v1.0.pdf

• I accept the above linked CLA.

[lysyi3m]

@td202 hey! 👋🏻 as a follow up for #169, here I have another endpoint suggestion. Let me know if you think it needs to be updated.

Thanks in advance! 🍻

[DOBEN]

Thanks for your contribution @lysyi3m! It looks good.