docs: remove NFT Aggregator section (#469)

Remove the build/indexer/nft-aggregator documentation section (overview,
analytics/GraphQL APIs, table reference, and marketplace pages) along with
its sidebar group and navigation labels (en/zh).

- Delete src/content/docs/build/indexer/nft-aggregator/ and nft-aggregator.mdx
- Remove the sidebar group in astro.sidebar.ts
- Remove the nav labels in src/content/nav/en.ts and zh.ts
- Update the migration pointer in indexer-reference.mdx (nft_marketplace_v2_*)
- Add vercel.json redirects from the removed URLs to /build/indexer

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: jtang17

astro.sidebar.ts

@@ -371,26 +371,6 @@ export const sidebar = [
               }),
             ],
           }),
-          group("build.group.indexer.nft-aggregator", {
-            collapsed: true,
-            items: [
-              "build/indexer/nft-aggregator",
-              "build/indexer/nft-aggregator/analytics-api",
-              "build/indexer/nft-aggregator/graphql-api",
-              "build/indexer/nft-aggregator/marketplaces",
-              "build/indexer/nft-aggregator/nft-aggregator-table",
-              group("build.group.indexer.nft-aggregator.marketplaces", {
-                collapsed: true,
-                items: [
-                  "build/indexer/nft-aggregator/marketplaces/bluemove",
-                  "build/indexer/nft-aggregator/marketplaces/rarible",
-                  "build/indexer/nft-aggregator/marketplaces/topaz",
-                  "build/indexer/nft-aggregator/marketplaces/tradeport",
-                  "build/indexer/nft-aggregator/marketplaces/wapal",
-                ],
-              }),
-            ],
-          }),
           group("build.group.indexer.txn-stream", {
             collapsed: true,
             items: [

src/content/docs/build/indexer/indexer-api/indexer-reference.mdx

@@ -584,7 +584,7 @@ The following tables are planned for deprecation, or are already deprecated. See
 | events\_view                            | To query custom events, you should create a [No-Code Indexer](https://geomi.dev/docs/no-code-indexing)                                                          |
 | move\_resources                         | Replace with account\_transactions                                                                                                                              |
 | move\_resources\_view                   | Replace with account\_transactions                                                                                                                              |
-| nft\_marketplace\_v2\_\*                | Replace with [NFT Aggregator API](/build/indexer/nft-aggregator)                                                                                                |
+| nft\_marketplace\_v2\_\*                | No direct replacement; query marketplace activity via the [Indexer API](/build/indexer/indexer-api)                                                             |
 | token\_activities                       | Replace with token\_activities\_v2                                                                                                                              |
 | token\_datas                            | Replace with current\_token\_datas\_v2                                                                                                                          |
 | token\_ownerships                       | Replace with current\_token\_ownerships\_v2                                                                                                                     |