Redesign login page with photo background and sign-up flow

[Copilot]

Implements new login page UI matching the provided design spec. Adds sign-up button and informational content while preserving existing OAuth flow.

Visual Changes

• Background: ImageBackground with existing banner assets + dark overlay (0.7/0.5 opacity for dark/light mode)
• Layout: Bottom-aligned content with bank icon in red container, welcome text, description
• Status bar: Black background (consistent with overlay)

New Functionality

• "What's HCB?" link: Opens fiscal sponsorship page via expo-web-browser
• Sign up button: Opens https://hcb.hackclub.com/users/auth?signup=true in-app
• Log in button: Restyled to outline variant (red border, white text), maintains OAuth flow

Key Implementation

<ImageBackground source={isDark ? banner-dark : banner-light}>
  <View style={overlay}>
    <Icon glyph="bank-account" />
    <Text>Welcome to <Text>HCB</Text>.</Text>
    <Text>Over 5,000 nonprofit projects...</Text>
    <Pressable onPress={() => WebBrowser.openBrowserAsync(...)}>
      <Text>What's HCB? →</Text>
    </Pressable>
    <Button variant="outline" color="#FFFFFF">Log in</Button>
    <Button variant="primary">Sign up</Button>
  </View>
</ImageBackground>

White text throughout for contrast against photo background. Theme-aware via banner selection and overlay opacity.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• github-production-user-asset-6210df.s3.amazonaws.com
  • Triggering command: curl -L REDACTED -o /tmp/login-design.png (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>New Login Page UI</issue_title>
<issue_description>Rework the login page to look like the image below. Make sure to satisfy both dark & light mode requirements. When click "what's HCB" it should open an in app browser to https://hackclub.com/fiscal-sponsorship/ Sign up should go to https://hcb.hackclub.com/users/auth?signup=true and login should use the existing oauth flow without changing any of its functionality

</issue_description>

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

• Fixes New Login Page UI #274

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