Consolidate frontend REST calls with GraphQL

Replace 5 separate REST calls on home page load with a single GraphQL
query. Add homeData store that fetches posts, favorites, activities,
spotify, and auth in one request. Convert all admin mutations and
auth flows to use GraphQL. Add album images to Spotify GraphQL schema.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/graph/model/models_gen.go

@@ -0,0 +1,80 @@
+// Code generated by github.com/99designs/gqlgen, DO NOT EDIT.
+
+package model
+
+import (
+	"time"
+
+	"adam-french.co.uk/backend/models"
+)
+
+type AuthPayload struct {
+	User *models.User `json:"user"`
+}
+
+type CreateActivityInput struct {
+	Type string  `json:"type"`
+	Name string  `json:"name"`
+	Link *string `json:"link,omitempty"`
+}
+
+type CreateFavoriteInput struct {
+	Type string  `json:"type"`
+	Name string  `json:"name"`
+	Link *string `json:"link,omitempty"`
+}
+
+type CreatePostInput struct {
+	Title   string `json:"title"`
+	Content string `json:"content"`
+}
+
+type CreateUserInput struct {
+	Username string `json:"username"`
+	Password string `json:"password"`
+}
+
+type LoginInput struct {
+	Username string `json:"username"`
+	Password string `json:"password"`
+}
+
+type Mutation struct {
+}
+
+type Query struct {
+}
+
+type SpotifyAlbum struct {
+	Name   string          `json:"name"`
+	Images []*SpotifyImage `json:"images"`
+}
+
+type SpotifyArtist struct {
+	Name string `json:"name"`
+}
+
+type SpotifyImage struct {
+	URL string `json:"url"`
+}
+
+type SpotifyPlaying struct {
+	Playing bool          `json:"playing"`
+	Track   *SpotifyTrack `json:"track,omitempty"`
+}
+
+type SpotifyRecentItem struct {
+	Track    *SpotifyTrack `json:"track"`
+	PlayedAt time.Time     `json:"playedAt"`
+}
+
+type SpotifyTrack struct {
+	Name    string           `json:"name"`
+	Artists []*SpotifyArtist `json:"artists"`
+	Album   *SpotifyAlbum    `json:"album"`
+}
+
+type UpdatePostInput struct {
+	Title   string `json:"title"`
+	Content string `json:"content"`
+}