test: expand data source API coverage

[yyqdbngt]

Motivation

The data source API tests covered the happy paths of load/create/update, the multi-page export, and delete/test basics, but left authenticated connections, bearer tokens, short last pages, and the max-page guard untested. This PR grows the suite from 3 to 7 cases.

Changes

• testDataSource forwards username/password for basic-auth sources and bearerToken for token-auth sources.
• listAllDataSources stops early when the last page comes back short (fewer items than the declared total).
• listAllDataSources throws Data source export exceeded 100 pages when pages keep returning full inventories.

Verification

• vitest run src/api/settings.test.ts: 7/7 passed
• tsc --noEmit: clean
• eslint src/api/settings.test.ts: clean

[RockteMQ-AI]

Summary

Expands data source API test coverage from 3 to 7 cases — adds authenticated/bearer token test paths, early pagination termination, and max-page guard.

LGTM — thorough coverage of pagination edge cases and auth forwarding.

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