fix: resolve production bugs, improve code quality, and add test suite

[olcar]

• Fix PATCH data corruption (originPlanet/character undefined queries)
• Fix DELETE soft-delete (was a no-op for characters)
• Fix auth typo (acces_token → access_token)
• Strip password hash from register response
• Remove 10-day Cache-Control on API responses
• Remove X-Powered-By header
• Fix ESLint config and remove 12 unused imports
• Add synchronization warnings for production
• Add .env.example for easier onboarding
• 28 unit tests across all 4 services
• 4 e2e tests replacing broken placeholder
• Rewrite README with project-specific documentation

[olcar]

Hello! Please let me know what you think of those improvements suggestions :)

[intentodepirata]

Thanks for the contribution. The PATCH/DELETE fixes match the API’s original behavior and the unit tests pass.

Before merging, could you fix and test isDestroyed with multipart/form-data? Form-data sends values such as "false" as strings, while the DTO now requires a runtime boolean, so valid create/update requests may be rejected.

Once that case is covered, this should be ready from my side.