refactor(frontend): remove logger-client dependency on authStore

[test3207]

Parent Issue

Epic 3.5: Observability & Operations (#190)

Summary

Refactor logger-client.ts to remove its dependency on authStore, breaking the circular dependency and improving bundle size.

Problem

The initial logger implementation (#250) had logger-client.ts importing authStore to get userId. This caused:

1. Circular dependency: authStore -> logger -> authStore
2. Vite warnings during build
3. Bundle optimization issues (dynamic imports not effective)

Solution

• Remove authStore dependency from logger-client.ts
• Add userId field to LogOptions interface
• Callers pass userId via { userId: getUserId() }
• Each store defines a simple getUserId() helper

Changes

File	Change
frontend/src/lib/logger-client.ts	Remove authStore import, add userId to LogOptions
frontend/src/stores/authStore.ts	Pass userId in logger calls
frontend/src/stores/libraryStore.ts	Add getUserId() helper, pass userId in logger calls
frontend/src/stores/playlistStore.ts	Add getUserId() helper, pass userId in logger calls
frontend/src/stores/playerStore/persistence.ts	Add getUserId() helper, pass userId in logger calls

Bundle Impact

Metric	Before (v2.0.2-rc.5)	After	Delta
Main bundle	293.03 KB	301.10 KB	+8.07 KB
Main gzip	91.31 KB	93.63 KB	+2.32 KB

The ~8 KB increase is the total cost of the logging system (logger-client.ts + userId tracking in stores). This is acceptable for production observability.

Acceptance Criteria

• No Vite circular dependency warnings
• All tests pass (411 frontend tests)
• Build succeeds without warnings
• Logger has no business dependencies (pure utility)