[P3] Add unit tests for JwtStrategy.validate()

[cyber-punk112]

Description

src/auth/jwt.strategy.ts defines JwtStrategy.validate(payload), which returns { sub: payload.sub, publicKey: payload.publicKey ?? payload.sub } — falling back to sub when publicKey is missing from the token payload. There is no jwt.strategy.spec.ts file anywhere in the repo, so this fallback logic (which several other tests rely on implicitly when signing test JWTs with only sub) has no dedicated unit test.

Deliverables

• Create src/auth/jwt.strategy.spec.ts
• Test validate() with a payload containing both sub and publicKey
• Test validate() with a payload containing only sub, asserting publicKey falls back to it
• npm run build passes

[Uneks-mama]

@Uneks-mama has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer I would like to work on this issue

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[victor-2017]

@victor-2017 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

i would like to take this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @victor-2017 to this issue.