feat: connectivity view: quota for all transports (#7630)

- **show quota of all relays**
- **remove `DC_STR_STORAGE_ON_DOMAIN` stock string**
- renames the quota section to "Relay Capacity" until we come up with a
better name in
https://github.com/chatmail/core/issues/7580#issuecomment-3633803432

closes #7591

<img width="300" alt="image"
src="https://github.com/user-attachments/assets/1909dccd-e6b3-42e6-963f-004b2b464db7"
/> <img width="300" alt="image"
src="https://github.com/user-attachments/assets/1e97e67b-e0ed-492b-95a0-6ef12595abe4"
/>

src/stock_str.rs

@@ -1144,14 +1144,6 @@ pub(crate) async fn outgoing_messages(context: &Context) -> String {
     translated(context, StockMessage::OutgoingMessages).await
 }
 
-/// Stock string: `Storage on %1$s`.
-/// `%1$s` will be replaced by the domain of the configured email-address.
-pub(crate) async fn storage_on_domain(context: &Context, domain: &str) -> String {
-    translated(context, StockMessage::StorageOnDomain)
-        .await
-        .replace1(domain)
-}
-
 /// Stock string: `Not connected`.
 pub(crate) async fn not_connected(context: &Context) -> String {
     translated(context, StockMessage::NotConnected).await