Add Plex integration icons and improve authentication flow

- Create IconPlex with play button symbol for Plex login button
- Create IconServer for server information display
- Create IconSync for library sync operations
- Replace inline SVGs with icon components in PlexAuthButton
- Replace inline SVGs with icon components in PlexServerInfo
- Add MissingPlexAuthPage for better auth error handling
- Update routes to redirect missing Plex auth to dedicated page
- Refactor usePlexApi and usePlexAuth for better composable patterns
- Remove deprecated usePlexLibraries composable
- Improve PlexLibraryModal and PlexLibraryStats components
- Clean up Plex-related helper utilities

src/pages/MissingPlexAuthPage.vue

@@ -0,0 +1,53 @@
+<template>
+  <div class="not-authenticated">
+    <h1><IconStop /> Must be authenticated with Plex</h1>
+    <p>Go to Settings to link your Plex account</p>
+  </div>
+</template>
+
+<script setup lang="ts">
+  import IconStop from "@/icons/IconStop.vue";
+</script>
+
+<style lang="scss" scoped>
+  @import "scss/media-queries";
+
+  .not-authenticated {
+    padding: 2rem;
+    text-align: center;
+
+    h1 {
+      display: flex;
+      align-items: center;
+      justify-content: center;
+      font-size: 3rem;
+      margin-bottom: 1rem;
+
+      svg {
+        margin-right: 1rem;
+        height: 3rem;
+        width: 3rem;
+      }
+    }
+
+    p {
+      font-size: 1.2rem;
+      color: var(--text-color-60);
+    }
+
+    @include mobile {
+      padding: 1rem;
+      padding-right: 0;
+
+      h1 {
+        font-size: 1.65rem;
+
+        svg {
+          margin-right: 1rem;
+          height: 2rem;
+          width: 2rem;
+        }
+      }
+    }
+  }
+</style>