Fix inconsistent logo & title size on login page

[Copilot]

The login page auth-header used Bootstrap h3 (~28px) for mode titles ("Sign In", etc.), while the homepage navbar renders the branding at 22px — making the logo and title visually inconsistent across pages.

Changes

• login_view.php: Replaced the per-mode <h1 class="h3"> headings in auth-header with the actual site logo + "HeatpumpMonitor.org" branding, matching the homepage navbar markup and sizing exactly. Mode-specific context is retained as a subtitle <p>.
• Added .auth-brand and .auth-brand-logo CSS classes mirroring .navbar-brand / .navbar-brand-logo from theme.php (font-size: 22px, 36×36px logo).

<a class="auth-brand text-white text-decoration-none" href="<?php echo $path; ?>">
    <img src="<?php echo $path; ?>theme/img/logo/apple-touch-icon.png" alt="HeatpumpMonitor Logo" class="auth-brand-logo">
    <span><b>HeatpumpMonitor</b>.org</span>
</a>

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Logo & title inconsistant size</issue_title>
<issue_description>On the login page the site Logo and Title has a larger font compared to the homepage:

Large front:
https://heatpumpmonitor.org/user/login

Smaller font:
https://heatpumpmonitor.org/

The Title and logo sizes hold be consistent
</issue_description>

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

• Fixes Logo & title inconsistant size #143

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