fix: update MegaETH explorer display name to Megaeth Explorer (#27592)

## **Description**

Updates the MegaETH block explorer button text from "View on Megaeth" to
"View on Megaeth Explorer" in the
Receive flow.
Adds a `BLOCK_EXPLORER_NAME_OVERRIDES` map in
`app/util/networks/index.js` that overrides the auto-derived
explorer name for `megaeth.blockscout.com`. Only MegaETH is affected;
all other networks continue using the
existing hostname-based auto-derivation logic.
## **Changelog**                                          

CHANGELOG entry: Fixed MegaETH explorer button to display "View on
Megaeth Explorer" instead of "View on
Megaeth"
## **Related issues**
                            
Fixes:

## **Manual testing steps**

```gherkin
Feature: MegaETH explorer button wording

Scenario: user views receive address for ETH on MegaETH                                                   
Given user has MegaETH network added
                                                                              
When user selects ETH on MegaETH and taps Receive                                                       
Then the button at the bottom reads "View on Megaeth Explorer"                                          
                                                                              
Scenario: other networks are unaffected                                                                
Given user has other networks added                                                                     
                                                                              
When user selects a token on another network and taps Receive                                           
Then the explorer button text remains unchanged
```                                                         
Screenshots/Recordings
Before

<img width="463" height="763" alt="image"
src="https://github.com/user-attachments/assets/776ec304-d1bf-4bf2-b043-769122635d93"
/>
                            
"View on Megaeth"

After

<img width="1206" height="2622" alt="image"
src="https://github.com/user-attachments/assets/5725e342-b118-4f11-969e-8ddd2b1ce0f6"
/>


"View on Megaeth Explorer"

Pre-merge author checklist

- [x] I've followed https://github.com/MetaMask/contributor-docs and
https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md.
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using https://jsdoc.app/ format if
applicable
- [x] I've applied the right labels on the PR (see
https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md).
Not equired for external contributors.

                                                           
Pre-merge reviewer checklist
                            

- [x] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [x] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes

the necessary testing evidence such as recordings and or screenshots.



<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk string-only change: adds a hostname-specific override for one
block explorer name, leaving existing hostname-derived naming for all
other explorers unchanged.
> 
> **Overview**
> Updates `getBlockExplorerName` to support hostname-specific
display-name overrides via a new `BLOCK_EXPLORER_NAME_OVERRIDES` map.
> 
> This ensures `megaeth.blockscout.com` is shown as **"MegaETH
Explorer"** (e.g., in “View on …” buttons) instead of relying on the
default subdomain-based capitalization.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
dad1e7e. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: jeremytsng

app/util/networks/index.js

@@ -496,6 +496,14 @@ export function compareRpcUrls(rpcOne, rpcTwo) {
   return false;
 }
 
+/**
+ * Hostname-to-display-name overrides for block explorers whose
+ * auto-derived name (first subdomain, capitalised) is not ideal.
+ */
+const BLOCK_EXPLORER_NAME_OVERRIDES = {
+  'megaeth.blockscout.com': 'MegaETH Explorer',
+};
+
 /**
  * From block explorer url, get rendereable name or undefined
  *
@@ -505,6 +513,14 @@ export function getBlockExplorerName(blockExplorerUrl) {
   if (!blockExplorerUrl) return undefined;
   const hostname = new URL(blockExplorerUrl).hostname;
   if (!hostname) return undefined;
+  if (
+    Object.prototype.hasOwnProperty.call(
+      BLOCK_EXPLORER_NAME_OVERRIDES,
+      hostname,
+    )
+  ) {
+    return BLOCK_EXPLORER_NAME_OVERRIDES[hostname];
+  }
   const tempBlockExplorerName = fastSplit(hostname);
   if (!tempBlockExplorerName || !tempBlockExplorerName[0]) return undefined;
   return (