Fix satellite-admin to use Spanner with db selector

[Copilot]

When running storj-up init db,core,admin,minimal, satellite-admin was connecting to CockroachDB while satellite-api and satellite-core correctly used Spanner. The db selector deploys Spanner, not CockroachDB.

Changes

Updated pkg/recipe/admin.yaml:

• STORJ_DATABASE: cockroach → spanner environment reference
• STORJ_METAINFO_DATABASE_URL: cockroach → spanner environment reference
• Added missing SPANNER_EMULATOR_HOST configuration

This aligns satellite-admin with satellite-api and satellite-core. Using the explicit cockroach selector still works as expected.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Admin is still using cockroach DB by default</issue_title>
<issue_description>After running storj-up init db,core,admin,minimal admin service have crdb DB and rest of services is using Spanner.

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Admin is still using cockroach DB by default #118

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