Refactor mobile chat into modal (#3038)

* feat(mobile): refactor mobile chat into modal

- Make page always scrollable
- Move mobile chat into a standalone modal

* fix(test): split out mobile browser test specs

* fix(mobile): force chat button to render on top of footer

* fix: some small updates from review

* fix: hide/show hide chat menu option based on width

* fix: chat button icon getting cut off

* chore(tests): add browser tests for mobile chat modal

* chore(tests): add story for ChatModal component

* fix(test): quiet shellcheck

* fix: remove unused import

* fix(tests): silence storybook linting warning

* fix(ui): reposition chat modal button icon with transform

web/components/layouts/Main/Main.module.scss

@@ -4,7 +4,7 @@
   // this margin is for fixed header
   padding-top: var(--header-height);
   background-color: var(--theme-color-main-background);
-  min-height: 100dvh;
+  min-height: 100vh;
 
   position: relative;