feat(grading): support in-memory PGlite backend for grading endpoints

[simonmysun]

Grading endpoints previously rejected PGlite connections with a 400
GRADING_PGLITE_NOT_SUPPORTED because the comparators were hard-wired to
a TypeORM DataSource. Route PGlite connections through the shared
pgliteInstances registry so /grade and /compare/* run end-to-end without
an external PostgreSQL server.

[Copilot]

Pull request overview

Enables the SQL assessment service grading endpoints to run end-to-end against an in-process PGlite database by routing query execution through a shared pgliteInstances registry and a backend-agnostic RowQueryFn, rather than requiring a TypeORM DataSource (external Postgres).

Changes:

• Introduces RowQueryFn + makePGliteRowQueryFn and refactors grading comparators/services to execute queries via this backend-agnostic function.
• Updates GradingController to resolve either Postgres or PGlite connections and to use a unified cleanup hook (no-op for shared PGlite).
• Adds unit/integration tests and extends the smoke test script to cover grading endpoints on PGlite; removes the deprecated GRADING_PGLITE_NOT_SUPPORTED message.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
services/sql-assessment-service/src/shared/utils/database-utils.ts	Adds RowQueryFn abstraction plus makePGliteRowQueryFn and PGlite key generation.
services/sql-assessment-service/src/grading/result-set-comparator.ts	Refactors result-set comparison/executability checks to use RowQueryFn and normalizes DB error extraction.
services/sql-assessment-service/src/grading/query-grading-service.ts	Threads RowQueryFn through the grading pipeline instead of a DataSource.
services/sql-assessment-service/src/grading/comparators/execution-plan-comparator.ts	Refactors EXPLAIN plan retrieval to execute via RowQueryFn.
services/sql-assessment-service/src/grading/grading-controller.ts	Adds PGlite backend resolution, shared-instance handling, and unified cleanup across endpoints.
services/sql-assessment-service/src/shared/i18n/messages.ts	Removes GRADING_PGLITE_NOT_SUPPORTED message key and translations.
services/sql-assessment-service/test/shared/pglite-row-query-fn.test.ts	Adds unit tests for PGlite RowQueryFn shape invariants and comparator integration.
services/sql-assessment-service/test/grading/pglite-grading-controller.test.ts	Adds integration tests for grading + compare endpoints backed by PGlite.
services/sql-assessment-service/scripts/smoke-test.sh	Adds smoke coverage for grading endpoints on PGlite.

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[plc-dev]

Other than the type issue I would say this is fine to merge. So not necessarily a change request, rather a request to confirm the types are synced and only if they are not synced, a change to synchronize the types is required.