Add environment config loader and validation

[pragmaticAweds]

Repository

This issue belongs in Fundable-Protocol/Backend under indexer/.

Migrated from https://github.com/Fundable-Protocol/stellar_indexer/issues/2.

Context

Runtime configuration should be typed and validated before DB, poller, and API code depend on it.

Scope

• Add a config loader in common
• Validate required environment variables
• Parse numeric values like PORT, POLL_INTERVAL_MS, and START_LEDGER
• Add tests for valid and invalid config

Out of Scope

• Connecting to PostgreSQL
• Creating Soroban RPC clients
• Loading contract YAML files

Acceptance Criteria

• Missing required config fails with a clear error
• Invalid numeric config fails with a clear error
• Valid config returns typed values
• bun run type-check passes
• bun run test passes
• bun run lint passes
• bun run indexer:type-check passes
• bun run indexer:test passes
• bun run indexer:lint passes

Dependencies

• Add database dependency and migration tooling #20 is helpful but not strictly required

Suggested Files or Packages

• indexer/common/src/config/
• .env.example

[Nuel-ship-it]

@Nuel-ship-it has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, i would like to work on this issue

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[Chigybillionz]

@Chigybillionz has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I can take this up and deliver a fix. Please assign.

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[0xElyte]

@0xElyte has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I'd love to resolve this fast

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[promisszn]

@promisszn has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi i'd like to work on this

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[drips-wave]

Congratulations, @promisszn! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @promisszn: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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