Fix manifest purges and package version pages

Fix manifest purges for bucket-backed responses (19ad24d)

Publishing and description updates now purge the lb’s namespaced cache key for meta.json and npm version manifests, instead of only purging the public URL. This fixes a stale-cache bug where freshly published manifests could stay invisible to resolvers even after publish.

Show package version pages instead of redirecting away (3f7101b)

The package overview page now renders for non-latest versions again, instead of being treated like a doc route and redirecting to the latest docs. This restores access to historical version pages from the Versions tab while keeping the latest-version redirect behavior for actual doc endpoints.

Speed up API Docker builds with a shared registry cache (12b01b0)

The API image build switches from branch-scoped GitHub Actions cache storage to a registry-backed cache that survives merge-queue refs and is reusable across runs. That should cut repeated Docker build time substantially on CI.

Other misc changes

• Upgraded deno_graph to 0.111.0 and deno_doc to 0.207.0; also removed now-unneeded unstable_text_imports flags.
• Local symbol search typing/filtering cleanup to match the docs data shape.