style: redo scoped styles (#1671)

# Motivation

In #1666 we have moved scoped styles to global style to workaround the build reproducibility of SvelteKit+ViteJS [#8291](sveltejs/kit#8291).

This PR redo the changes has #1670 will solve the reproducibility issue by removing the unused vite manifest file from our build results.

# PRs

- [x] #1670

# Changes

- redo scoped style and remove related global style

frontend/src/lib/pages/SignInAccounts.svelte

@@ -5,7 +5,7 @@
   // TODO(GIX-1071): this static pre-rendering component should be improved with some more information and shiny design
 </script>
 
-<main class="sign-in">
+<main>
   <h1>{$i18n.auth_accounts.title}</h1>
 
   <p>
@@ -14,3 +14,16 @@
 
   <SignIn />
 </main>
+
+<style lang="scss">
+  main {
+    display: flex;
+    flex-direction: column;
+  }
+  h1 {
+    line-height: var(--line-height-standard);
+  }
+  p {
+    margin-bottom: var(--padding-3x);
+  }
+</style>

frontend/src/lib/pages/SignInCanisters.svelte

@@ -5,7 +5,7 @@
   // TODO(GIX-1071): this static pre-rendering component should be improved with some more information and shiny design
 </script>
 
-<main class="sign-in">
+<main>
   <h1>{$i18n.auth_canisters.title}</h1>
 
   <p>
@@ -14,3 +14,16 @@
 
   <SignIn />
 </main>
+
+<style lang="scss">
+  main {
+    display: flex;
+    flex-direction: column;
+  }
+  h1 {
+    line-height: var(--line-height-standard);
+  }
+  p {
+    margin-bottom: var(--padding-3x);
+  }
+</style>

frontend/src/lib/pages/SignInNeurons.svelte

@@ -5,7 +5,7 @@
   // TODO(GIX-1071): this static pre-rendering component should be improved with some more information and shiny design
 </script>
 
-<main class="sign-in">
+<main>
   <h1>{$i18n.auth_neurons.title}</h1>
 
   <p>
@@ -14,3 +14,16 @@
 
   <SignIn />
 </main>
+
+<style lang="scss">
+  main {
+    display: flex;
+    flex-direction: column;
+  }
+  h1 {
+    line-height: var(--line-height-standard);
+  }
+  p {
+    margin-bottom: var(--padding-3x);
+  }
+</style>

frontend/src/routes/+layout.svelte

@@ -50,6 +50,5 @@
 <style lang="scss" global>
   @import "@dfinity/gix-components/styles/global.scss";
   @import "../lib/themes/legacy";
-  @import "../lib/themes/global";
   @import "../lib/themes/variables";
 </style>