Fix "Back to today" button not reloading active tab data

[Copilot]

Clicking "Back to today" while on any tab other than the dashboard (e.g. habits) updated the date display but left the tab content stale — it was only re-rendering the dashboard.

Root Cause

The goTodayBtn handler called this.render(), which unconditionally calls renderDashboard(). The date arrow buttons go through navigateDate(), which correctly resolves the active tab and calls switchTab().

Fix

Align goTodayBtn with the navigateDate() pattern — read the active tab and dispatch to switchTab():

// Before
this.render();

// After
const activeTabName = (document.querySelector('.nav-tab.active') as HTMLElement | null)?.dataset.tab;
if (activeTabName) {
    this.switchTab(activeTabName);
} else {
    this.renderDashboard();
}

Tests

Added an E2E test verifying that the habits tab remains active and visible after navigating to a previous day and clicking "Back to today".

Original prompt

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This section details on the original issue you should resolve

<issue_title>Back to today link doesn't reload data</issue_title>
<issue_description>When going to a previous day to check off completed habits, clicking the "Back to today" button keeps all the same data unless you go back a day and then forward to the current day again using the date selection arrows</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Back to today link doesn't reload data #20

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