Declare dotenv, remove unused deps, fix @jest/globals, audit fixes

[monique-7arch]

Closes #1389
Closes #1390
Closes #1391
Closes #1392

• package.json: declared dotenv (^16.4.5, used by data-source.ts); removed @nestjs/mapped-types, iterare and ts-loader after a text search found no usage
• indexer.service.spec.ts: dropped the undeclared @jest/globals import so the spec uses the ambient jest globals like the others
• package-lock.json: regenerated and npm audit fix applied, lockfile only (--package-lock-only, nothing installed). Production audit goes from 24 vulnerabilities (1 critical, 13 high) to 4 (2 moderate, 2 high): the critical is gone. What remains is axios via @stellar/stellar-sdk@16, which only a major @stellar/stellar-sdk 17 bump fixes; left for a separate change.

Build, tests and e2e were not run.

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