[FRONTEND] Newsletter signup component (Mailchimp embed)

[sswez02]

Is your feature request related to a problem? Please describe.

AYO has a Mailchimp database of 1700+ subscribers with strong engagement (61.8% open rate). The new website needs a way for visitors to subscribe to the newsletter.

Describe the solution you'd like

• Build a newsletter signup component that integrates with Mailchimp
• Simple form: email address input + "Subscribe" button. Optional: first name field
• Use Mailchimp's embedded form or their signup form URL (check which approach the client's Mailchimp plan supports)
• Success/error states: show confirmation message on submit, handle errors gracefully
• Place the component in the Footer and/or as a standalone section on the Contact page
• Style to match the site design (don't use Mailchimp's default unstyled embed)

Describe alternatives you've considered

Could build a custom form that hits the Mailchimp API directly, but the embedded form approach is simpler and doesn't require API keys for M1. API integration can be a M2 enhancement if needed.

Additional context

Client has an existing Mailchimp setup. Ask them for the Mailchimp audience ID or embedded form code. The client also asked about displaying past newsletters on the site (thumbnails with links to Mailchimp archives) but that's out of scope for M1.

BEFORE MERGING

• Storybooks created where possible
• Tested with react testing library
• Tests written for critical interactions
• PR Reviewed (For non-trivial changes)
• Changes tested after rebasing on master or merging in master (hint: git fetch origin master:master, then git rebase master or git merge master)
• All required PR checks passing