feat(accounts): implement user accounts, sessions, and dashboards

Introduce Stage 4 features to support multi-user accounts, cookie-based web sessions, and personal dashboards.

Changes include:
- Adding `/register` to bootstrap the first admin account and `/login`/`/logout` for session management.
- Creating a personal dashboard (`/app`) to display owned boxes, storage usage, and upload history.
- Implementing admin user management (`/admin/users`) for generating invite links and managing user states.
- Updating the bbolt database schema to store users, sessions, invites, and collections.
- Adding `golang.org/x/crypto` for password hashing and introducing unit tests for account handlers.

backend/libs/handlers/pages.go

@@ -3,19 +3,38 @@ package handlers
 import (
 	"net/http"
 
+	"warpbox.dev/backend/libs/services"
 	"warpbox.dev/backend/libs/web"
 )
 
 type homeData struct {
 	MaxUploadSize string
+	Collections   []collectionView
+	IsAdmin       bool
 }
 
 func (a *App) Home(w http.ResponseWriter, r *http.Request) {
+	currentUser := a.currentPublicUser(r)
+	var collections []collectionView
+	var isAdmin bool
+	if user, ok := a.currentUser(r); ok {
+		isAdmin = user.Role == services.UserRoleAdmin
+		userCollections, err := a.authService.ListCollections(user.ID)
+		if err == nil {
+			collections = make([]collectionView, 0, len(userCollections))
+			for _, collection := range userCollections {
+				collections = append(collections, collectionView{ID: collection.ID, Name: collection.Name})
+			}
+		}
+	}
 	a.renderer.Render(w, http.StatusOK, "home.html", web.PageData{
 		Title:       "Upload your files",
 		Description: "Upload and share files through a self-hosted Warpbox instance.",
+		CurrentUser: currentUser,
 		Data: homeData{
 			MaxUploadSize: a.uploadService.MaxUploadSizeLabel(),
+			Collections:   collections,
+			IsAdmin:       isAdmin,
 		},
 	})
 }