[misaelalves99]

Fixes #1782.

Summary

The dashboard's Records & Sessions Trend chart previously relied on color and hover tooltips to identify its two data series.

This change:

• Adds a visible Recharts legend identifying Records and Sessions without requiring hover.
• Localizes series names in English, Spanish, and French.
• Differentiates Records and Sessions through solid and dashed line styles.
• Adds unit and Playwright regression tests for the legend.

Validation

• Targeted unit tests: 34/34 passed.
• Dashboard Playwright suite: 12/12 passed in Chromium.
• Global unit tests: 4,348 passed, with four expected failures.
• Instrumented coverage: 100% statements, branches, functions, and lines.
• Read-only lint-equivalent validation: 27/27 tasks passed. The literal root pnpm lint command was not run because it can invoke code-modifying generators or fixers.

Known E2E environment limitation

The isolated full Playwright run finished with 278 passed and 1 failed.

The sole failure was in testing/src/specs/record-file-deletion.spec.ts, which expected HTTP 201 when creating a FILE instrument record but received HTTP 503.

The isolated environment had STORAGE_ENABLED=false. Existing InstrumentRecordsService.create() logic explicitly rejects FILE records when storage is disabled.

This test is outside the files changed by this PR. The failure is documented as an environment/configuration limitation, and the complete E2E suite is not claimed to be passing.

A separate cross-browser smoke run produced 41/42 passes due to a Chromium subject-detail interaction timeout. A targeted Chromium rerun subsequently passed 7/7. The intermittent cause was not established.

Scope

Only three files are modified:

• apps/web/src/routes/_app/dashboard.tsx
• apps/web/src/routes/_app/__tests__/dashboard.test.tsx
• testing/src/specs/dashboard.spec.ts

No new dependencies or unrelated source changes.