Barrel Cleanup: Utility, Config, & Mock Packages Group

[nnoce14]

Goal: Remove barrel files/star re-exports from utility/config/mock packages: @cellix/typescript-config, @cellix/vitest-config, @cellix/mock-mongodb-memory-server, @cellix/mock-oauth2-server, @cellix/mongoose-seedwork, @cellix/api-services-spec. Add error-level Biome overrides for each. Refactor imports. Conflicts resolved via PR reviews.

Scope: packages/cellix/typescript-config, packages/cellix/vitest-config, packages/cellix/mock-mongodb-memory-server, packages/cellix/mock-oauth2-server, packages/cellix/mongoose-seedwork, packages/cellix/api-services-spec

Tasks:

• Audit index.ts and pure barrel patterns in each package
• Remove any barrels
• Refactor imports
• Add Biome error-level overrides per package
• Run lint/build/tests

Success Criteria:

• Packages have no barrels/star re-exports
• Biome config error override per package
• All builds/tests pass

Checklist:

• Audit barrels (all listed packages)
• Remove barrels/refactor imports
• Add Biome overrides
• Run verify