[WIP] Fix new event date/time picker not working in Firefox

[Copilot]

• Replace datetime-local input with separate date and time inputs for start_date
• Replace datetime-local input with separate date and time inputs for end_date
• Replace datetime-local input with separate date and time inputs for registration_close_date
• Add Stimulus controller to combine date and time inputs before submission
• Update spec to reflect new form structure
• Test the form manually to ensure it works in Firefox

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[maebeale]

@copilot try again