refactor(db): introduce DatabaseContext pattern for injectable db in tests

[aaight]

Summary

• Introduces a DatabaseContext class with a createDatabaseContext() factory that encapsulates the Drizzle db and pg pool, replacing the module-level let db / let pool singletons in src/db/client.ts
• Adds setDefaultDatabaseContext() as the proper DI mechanism for tests, replacing the _setTestDb() hack (kept as a deprecated backward-compat wrapper)
• Preserves all existing public APIs: getDb(), closeDb(), _setTestDb() — zero consumer changes needed
• Exports DrizzleDb type for use in typed DI scenarios
• Updates tests/helpers/sharedMocks.ts to expose setDefaultDatabaseContext and _setTestDb in mockDbClientModule
• Updates tests/unit/db/client.test.ts with full coverage of the new DatabaseContext, createDatabaseContext(), and setDefaultDatabaseContext() APIs

Card: https://trello.com/c/VAKnTLgw/531-as-a-developer-i-want-db-clientts-refactored-into-a-databasecontext-pattern-so-that-repositories-are-unit-testable-without-a-rea

Test plan

• npm test passes — 6596 tests across 344 test files, all green
• npm run typecheck passes — zero TypeScript errors
• biome check passes — zero lint errors
• tests/unit/db/client.test.ts — 21 tests including new coverage for setDefaultDatabaseContext, createDatabaseContext, and DatabaseContext class
• All existing repository tests continue to pass without modification (the getDb() mock in vi.mock('../../src/db/client.js') still works)

🤖 Generated with Claude Code

🕵️ claude-code · claude-sonnet-4-6 · run details

[codecov]

Codecov Report

❌ Patch coverage is 96.15385% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/db/client.ts	96.15%	2 Missing ⚠️

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[nhopeatall]

Summary

LGTM — Clean refactoring that introduces a DatabaseContext class wrapping the Drizzle db and pg pool, replacing module-level singletons with an injectable pattern. Backward compatibility is fully preserved: getDb(), closeDb(), and _setTestDb() all continue to work without consumer changes. CI is green across all 7 checks.

Notes

Minor comment inaccuracy (not blocking): The comment in closeDb() at src/db/client.ts:106-107 says "Only close if it's a real DatabaseContext / Skip if it was set via _setTestDb" — but the code doesn't skip anything. It unconditionally calls _defaultContext.close() and relies on the try/catch to handle mock contexts (whose close() is a no-op). The comment implies conditional behavior that doesn't exist. Consider simplifying to:

// close() is safe for both real pools and mock contexts (which have a no-op close)

Subtle behavior change (verified safe): The old closeDb() only reset pool/db but did NOT clear _testDbOverride. Now closeDb() nulls _defaultContext, which also clears any test override. This is safe because: (1) integration tests call _setTestDb(null) before closeDb(), and (2) unit tests call resetDbState() which does both. All 6596 tests pass, confirming no breakage.

🕵️ claude-code · claude-opus-4-6 · run details