[Medium] chore(repo): reject prod boot when JWT_SECRET is the placeholder value

[K1NGD4VID]

Context

.env.example ships JWT_SECRET=change_me_before_production. Safe as a placeholder but easy to leave in production. Enforce at boot.

Where

• File: .env.example
• Line: 212

Current Behavior

Placeholder value with no runtime guard.

Expected Behavior

In config/config.go, if STELLAR_NETWORK == 'PUBLIC' (or ENV == 'production') and JWT_SECRET == 'change_me_before_production', refuse to boot with a clear error.

Proposed Approach

1. Add a validation check in config/config.go.
2. Wire the check into the boot path.
3. Add a test.

Acceptance Criteria

• Prod boot with the placeholder fails fast
• Test-net / local boot still succeeds

Definition of Done

• PR links back with Closes #<this-issue-number>.

• CI is green (both Verify TypeScript Frontend & SDK and Verify Go Indexer & API jobs must pass).

• Local verification:

• cd indexer && go build -v ./... succeeds

• cd indexer && go vet ./... clean

• cd indexer && go test -v ./... green

• cd indexer && gofmt -l . prints nothing

Contributor Tips

• Indexer lives in indexer/ (Go 1.22, Postgres, subscribes to Soroban events).
• Run locally with docker compose up -d db && cd indexer && go run .
• Format with gofmt -w . and vet with go vet ./... before pushing.
• Test with cd indexer && go test -v ./....
• HTTP handlers must accept context.Context and honor cancellation.

Tech Stack

indexer

How to Claim

Comment .take (or say you're working on it) and open a PR with Closes #<this-issue-number> in the description.

Difficulty: Medium (complexity:medium) -- used for Drips Wave point allocation.