Add HealthCheckService to monitor web3 connection states

[not-reed]

Description

Added a HealthCheckService to monitor web3 connections and ensure clients are connected to the correct chain. The service runs periodic checks (currently set at 1-second intervals) to verify that the public client, wallet client, and injected client are all connected to the expected blockchain.

The service:

• Starts automatically when the iframe app initializes
• Compares the connected chain IDs against the expected chain
• Logs warnings when mismatches are detected
• Includes TODOs for future improvements like error correction and UI feedback

This is a first step toward improving connection reliability and providing better feedback when chain mismatches occur.

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Checklist

Basics

• B1. I have applied the proper label & proper branch name (e.g. norswap/build-system-caching).
• B2. This PR is not so big that it should be split & addresses only one concern.
• B3. The PR targets the lowest branch it can (ideally master).

Reminder: PR review guidelines

Correctness

• C1. Builds and passes tests.
• C2. The code is properly parameterized & compatible with different environments (e.g. local,
  testnet, mainnet, standalone wallet, ...).
• C3. I have manually tested my changes & connected features.

< INDICATE BROWSER, DEMO APP & OTHER ENV DETAILS USED FOR TESTING HERE >

< INDICATE TESTED SCENARIOS (USER INTERFACE INTERACTION, CODE FLOWS) HERE >

• C4. I have performed a thorough self-review of my code after submitting the PR,
  and have updated the code & comments accordingly.

Architecture & Documentation

• D1. I made it easy to reason locally about the code, by (1) using proper abstraction boundaries,
  (2) commenting these boundaries correctly, (3) adding inline comments for context when needed.
• D2. All public-facing APIs are documented in the docs.
  Public APIS and meaningful (non-local) internal APIs are properly documented in code comments.
• D3. If appropriate, the general architecture of the code is documented in a code comment or
  in a Markdown document.
• D4. An appropriate Changeset has been generated (and committed) with make changeset for
  breaking and meaningful changes in packages (not required for cleanups & refactors).

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[not-reed]

• Add HealthCheckService to monitor web3 connection states #764 👈 (View in Graphite)
• master

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