Correct compound modifiers in generated README descriptions

[coderabbitai]

Summary

Correct compound modifiers in the source descriptions that generate README documentation.

Required changes

• Change the src/app description to FastAPI-based web service.
• Change the src/authentication description to JWK-based JWT auth.
• Regenerate src/app/README.md and src/authentication/README.md after updating the source descriptions.

Rationale

Hyphenated compound modifiers improve grammar and maintain consistent generated documentation.

Affected areas

• Documentation source for src/app/README.md
• Documentation source for src/authentication/README.md
• Generated README files: src/app/README.md and src/authentication/README.md

Acceptance criteria

• The generated main.py entry in src/app/README.md contains Definition of FastAPI-based web service.
• The generated authentication entry contains JWK-based JWT auth.
• The README generator produces the corrected descriptions without manual edits to generated files.

Backlinks

• Pull request: LCORE-3444: Properly formatted devel doc #2367
• Review comment: LCORE-3444: Properly formatted devel doc #2367 (comment)
• Requested by: @tisnik