fix(frontend/test): add missing escapeHtmlAttr to utils mocks (Build frontend CI red)

[cristim]

Problem

frontend/src/plans.ts (11 call sites) and frontend/src/history.ts (6) use escapeHtmlAttr, but several test suites' jest.mock('../utils', () => ({ ... })) factories do not stub escapeHtmlAttr. When those tests render plans/history, the call throws:

TypeError: (0 , utils_1.escapeHtmlAttr) is not a function

This fails the "Build frontend" CI job (it runs the jest suites) on the base branch and on every frontend PR (e.g. visible on #1114, which only inherited it). plans.test.ts and the history-* suites are affected.

Fix

Add an escapeHtmlAttr stub to the jest.mock('../utils', …) factory in each affected suite, mirroring the real helper (escapes & < > " '). frontend/src/__tests__/history.test.ts already has a correct stub to copy.

Acceptance criteria

• Every frontend jest suite that renders plans/history mocks escapeHtmlAttr.
• jest frontend suites pass (the 2 pre-existing formatDate/getDateParts timezone failures are unrelated and out of scope).
• "Build frontend" CI goes green.