fix(studio): point Usage log ingest and query links at logs-* docs (#51001)

## Problem

The org Usage page links added in #50570 point to
`/docs/guides/platform/manage-your-usage/log-ingest` and `/log-query`.
Neither page exists. The docs live at `logs-ingest` and `logs-query`, so
every click from the Usage page lands on a 404. Within a day of #50570
shipping, these two paths were the top docs 404s by unique visitors.

## Solution

- Point both Usage page links at the `logs-*` pages.
- Add permanent redirects from the singular paths, because they're
already being shared: search engines and AI assistants now send people
to them. The existing generator in `apps/www/next.config.mjs` adds the
`.md` variants.

## To test

On the Vercel previews:
- [x] Open an org's Usage page on the Studio preview and click the Log
Ingestion docs link: expect the `logs-ingest` docs page, not a 404.
Opens `supabase.com/docs/guides/platform/manage-your-usage/logs-ingest`
in a new tab ("Manage Logs Ingest usage").
- [x] Click the Log Query docs link: expect the `logs-query` docs page.
Opens `.../logs-query` in a new tab ("Manage Logs Query usage").
- [x] No docs link on the Usage page still points at the singular
`log-ingest` or `log-query` paths.
- [x] On the www preview, request
`/docs/guides/platform/manage-your-usage/log-ingest` and `/log-query`:
expect a 308 to the `logs-*` pages. Both return 308 to the matching
`logs-*` path. The www preview doesn't serve `/docs`, so I confirmed
both targets return 200 on production.
- [x] `log-ingest.md` and `log-query.md` also return 308 to the matching
`logs-*.md` paths.

## Linear
- fixes GROWTH-1296


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Updated the Log Ingestion and Log Query documentation links to their
current pages.
* Added permanent redirects from the previous documentation paths to the
corresponding pages.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/studio/components/interfaces/Organization/Usage/Usage.constants.tsx

@@ -399,7 +399,7 @@ export const USAGE_CATEGORIES: (subscription?: OrgSubscription) => CategoryMeta[
           links: [
             {
               name: 'Log Ingestion',
-              url: `${DOCS_URL}/guides/platform/manage-your-usage/log-ingest`,
+              url: `${DOCS_URL}/guides/platform/manage-your-usage/logs-ingest`,
             },
           ],
         },
@@ -417,7 +417,7 @@ export const USAGE_CATEGORIES: (subscription?: OrgSubscription) => CategoryMeta[
           links: [
             {
               name: 'Log Query',
-              url: `${DOCS_URL}/guides/platform/manage-your-usage/log-query`,
+              url: `${DOCS_URL}/guides/platform/manage-your-usage/logs-query`,
             },
           ],
         },