web: new popup with meowbalt, fixes, removed migration popup

- new popup style featuring meowbalt
- removed migration popup
- rounder corners
- bottom glass-bkg in popups is no longer rounded on top right (accidentally matched as :last-child)
- small popup is now of fixed width on desktop
- small popup animation should be smoother on mobile
- better ui scaling across resolutions

src/localization/languages/en.json

@@ -16,7 +16,6 @@
         "AccessibilityOpenDonate": "open donation popup",
         "TitlePopupAbout": "what's cobalt?",
         "TitlePopupSettings": "settings",
-        "TitlePopupError": "uh-oh...",
         "TitlePopupChangelog": "what's new?",
         "TitlePopupDonate": "support cobalt",
         "TitlePopupDownload": "how to save?",

src/localization/languages/ru.json

@@ -16,7 +16,6 @@
         "AccessibilityOpenDonate": "сделать пожертвование",
         "TitlePopupAbout": "что за кобальт?",
         "TitlePopupSettings": "настройки",
-        "TitlePopupError": "опаньки...",
         "TitlePopupChangelog": "что нового?",
         "TitlePopupDonate": "поддержи кобальт",
         "TitlePopupDownload": "как сохранить?",