Require accepting ToS when enabling zeta (#23255)

Note: Design hasn't been reviewed yet, but the logic is done

When the user switches the inline completion provider to `zed`, we'll
show a modal prompting them to accept terms if they haven't done so:


https://github.com/user-attachments/assets/3fc6d368-c00a-4dcb-9484-fbbbb5eb859e

If they dismiss the modal, they'll be able to get to it again from the
inline completion button:


https://github.com/user-attachments/assets/cf842778-5538-4e06-9ed8-21579981cc47

This also stops zeta sending requests that will fail immediately when
ToS are not accepted.

Release Notes:

- N/A

---------

Co-authored-by: Richard <richard@zed.dev>
Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Joao <joao@zed.dev>

crates/ui/src/components/icon.rs

@@ -68,6 +68,8 @@ pub enum IconSize {
     #[default]
     /// 16px
     Medium,
+    /// 48px
+    XLarge,
 }
 
 impl IconSize {
@@ -77,6 +79,7 @@ impl IconSize {
             IconSize::XSmall => rems_from_px(12.),
             IconSize::Small => rems_from_px(14.),
             IconSize::Medium => rems_from_px(16.),
+            IconSize::XLarge => rems_from_px(48.),
         }
     }
 
@@ -92,6 +95,7 @@ impl IconSize {
             IconSize::XSmall => DynamicSpacing::Base02.px(cx),
             IconSize::Small => DynamicSpacing::Base02.px(cx),
             IconSize::Medium => DynamicSpacing::Base02.px(cx),
+            IconSize::XLarge => DynamicSpacing::Base02.px(cx),
         };
 
         (icon_size, padding)