chore: Notification controller eslint cleanup (#7484)

## Explanation

This PR addresses and removes ESLint suppressions in three files within
`packages/notification-services-controller/src/NotificationServicesPushController`.
The goal is to improve code quality and consistency by adhering to
established linting rules.

The changes include:
* **Adding explicit return types** to functions to satisfy
`@typescript-eslint/explicit-function-return-type`.
* **Using the nullish coalescing operator (`??`)** to fix
`@typescript-eslint/prefer-nullish-coalescing`.
* **Renaming short, non-descriptive identifiers** (e.g., `num` to
`numericValue`, `t` to `translate`, `n` to `notification`) to resolve
`id-denylist` and `id-length` violations.
* **Refactoring generic type parameters** (e.g., `N` to `TNotification`,
`K` to `TriggerType`/`TKey`) for better clarity and to fix
`@typescript-eslint/naming-convention`.
* **Adding an `eslint-disable` comment** with an explanation for the
`registration_token` property in `services.ts`. Its `snake_case` naming
is dictated by an external API contract, making a code change
impractical.
* **Removing all corresponding entries** from
`eslint-suppressions.json`.

## References

*   Fixes ASSETS-2100

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
(Functional tests pass, coverage thresholds are a separate issue)
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs)
- [ ] I've introduced [breaking
changes](https://github.com/MetaMask/core/tree/main/docs/breaking-changes.md)
in this PR and have prepared draft pull requests for clients and
consumer packages to resolve them

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Tightens TypeScript types and naming in
NotificationServicesPushController utilities/services, adds a justified
snake_case exception for `registration_token`, and removes related
ESLint suppressions.
> 
> - **Notification Services (push)**:
>   - `utils/get-notification-data.ts`:
> - Add explicit return types (`calcTokenAmount: BigNumber`,
`getLeadingZeroCount: number`, `formatAmount: string`, `getAmount:
string`).
> - Use nullish coalescing in parsing; type `handleShouldEllipse` and
options.
>     - Rename params/vars for clarity (e.g., `num` → `numericValue`).
>   - `utils/get-notification-message.ts`:
> - Strengthen generics and parameter names (`N/K` →
`TNotification/TKey`, `n` → `notification`, `t` → `translate`).
> - Add explicit return types across helpers and message creators; type
`getChainSymbol`.
>   - `services/services.ts`:
> - Document API contract and add ESLint naming exception for
`registration_token` in `PushTokenRequest`.
> - **Lint**:
> - Remove corresponding entries from `eslint-suppressions.json` for the
updated files.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
8dfbc12. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Cursor Agent <[email protected]>

Author: Prithpal-Sooriya

eslint-suppressions.json

@@ -1578,33 +1578,6 @@
       "count": 70
     }
   },
-  "packages/notification-services-controller/src/NotificationServicesPushController/services/services.ts": {
-    "@typescript-eslint/naming-convention": {
-      "count": 1
-    }
-  },
-  "packages/notification-services-controller/src/NotificationServicesPushController/utils/get-notification-data.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 5
-    },
-    "@typescript-eslint/prefer-nullish-coalescing": {
-      "count": 1
-    },
-    "id-denylist": {
-      "count": 1
-    }
-  },
-  "packages/notification-services-controller/src/NotificationServicesPushController/utils/get-notification-message.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 5
-    },
-    "@typescript-eslint/naming-convention": {
-      "count": 2
-    },
-    "id-length": {
-      "count": 9
-    }
-  },
   "packages/phishing-controller/src/BulkTokenScan.test.ts": {
     "@typescript-eslint/explicit-function-return-type": {
       "count": 2

packages/notification-services-controller/src/NotificationServicesPushController/services/services.ts

@@ -18,6 +18,8 @@ export type RegToken = {
  */
 export type PushTokenRequest = {
   addresses: string[];
+  // API response uses snake_case for this property
+  // eslint-disable-next-line @typescript-eslint/naming-convention
   registration_token: {
     token: string;
     platform: 'extension' | 'mobile' | 'portfolio';

packages/notification-services-controller/src/NotificationServicesPushController/utils/get-notification-data.ts

@@ -15,7 +15,7 @@ const defaultFormatOptions = {
  * @param decimals - The number of decimals to use for the calculation.
  * @returns The calculated token amount.
  */
-export function calcTokenAmount(value: string, decimals: number) {
+export function calcTokenAmount(value: string, decimals: number): BigNumber {
   const multiplier = Math.pow(10, Number(decimals || 0));
   return new BigNumber(String(value)).div(multiplier);
 }
@@ -28,14 +28,14 @@ export function calcTokenAmount(value: string, decimals: number) {
  * fractional part of the number. This is useful for determining the precision
  * of very small numbers.
  *
- * @param num - The number to analyze, which can be in the form
+ * @param numericValue - The number to analyze, which can be in the form
  * of a number or a string.
  * @returns The count of leading zeros in the fractional part of the number.
  */
-export const getLeadingZeroCount = (num: number | string) => {
-  const numToString = new BigNumber(num, 10).toString(10);
+export const getLeadingZeroCount = (numericValue: number | string): number => {
+  const numToString = new BigNumber(numericValue, 10).toString(10);
   const fractionalPart = numToString.split('.')[1] ?? '';
-  return fractionalPart.match(/^0*/u)?.[0]?.length || 0;
+  return fractionalPart.match(/^0*/u)?.[0]?.length ?? 0;
 };
 
 /**
@@ -50,15 +50,18 @@ export const getLeadingZeroCount = (num: number | string) => {
  * @param opts - The options to use when formatting
  * @returns The formatted number
  */
-export const formatAmount = (numericAmount: number, opts?: FormatOptions) => {
+export const formatAmount = (
+  numericAmount: number,
+  opts?: FormatOptions,
+): string => {
   // create options with defaults
   const options = { ...defaultFormatOptions, ...opts };
 
   const leadingZeros = getLeadingZeroCount(numericAmount);
   const isDecimal = numericAmount.toString().includes('.') || leadingZeros > 0;
   const isLargeNumber = numericAmount > 999;
 
-  const handleShouldEllipse = (decimalPlaces: number) =>
+  const handleShouldEllipse = (decimalPlaces: number): boolean =>
     Boolean(options?.shouldEllipse) && leadingZeros >= decimalPlaces;
 
   if (isLargeNumber) {
@@ -87,7 +90,7 @@ export const getAmount = (
   amount: string,
   decimals: string,
   options?: FormatOptions,
-) => {
+): string => {
   if (!amount || !decimals) {
     return '';
   }