[UI] fixes and improvements

[brookewp]

This fixes some issues that were caught by @stoph

• Added source name error handling — now a required field and can't add the same name as another source
• Added attributes to prevent 1password from suggesting passwords
• Removed overflow: hidden to prevent scroll issues (likely a temporary fix)

Airtable specific

• Adds validation to fields so only available fields can be selected
• Swapped out all fields for amount of fields for now

Screen.Recording.2024-12-17.at.8.17.14.PM.mov

Shopify specific

• 'store slug' to 'myshopify.com domain name' to match shopify docs
• entering link converts to subdomain