Adds authentication and pricing pages for user onboarding

Introduces comprehensive user authentication flow with plan selection and registration

Includes:
- Pricing page with plan details and selection
- Payment page with plan summary and card information
- Signup page for different plan tiers
- Shared authentication layout and design system improvements

Enhances user onboarding experience with clear plan information and streamlined signup process

PlanTempus.Application/Features/Accounts/Models/PlanInfo.cs

@@ -0,0 +1,101 @@
+namespace PlanTempus.Application.Features.Accounts.Models;
+
+public record PlanInfo(
+    string Key,
+    string Name,
+    string UserRange,
+    decimal? PricePerMonth,
+    string BadgeText,
+    string BadgeClass,
+    string BadgeIcon,
+    IReadOnlyList<string> Features,
+    bool RequiresPayment,
+    bool IsContactSales
+)
+{
+    public bool IsFree => PricePerMonth == 0;
+    public string PriceDisplay => PricePerMonth.HasValue ? $"{PricePerMonth:0}" : "Kontakt os";
+}
+
+public static class PlanCatalog
+{
+    private static readonly Dictionary<string, PlanInfo> Plans = new()
+    {
+        ["basis"] = new PlanInfo(
+            Key: "basis",
+            Name: "Basis",
+            UserRange: "1-3 brugere",
+            PricePerMonth: 0,
+            BadgeText: "Gratis",
+            BadgeClass: "free",
+            BadgeIcon: "ph-gift",
+            Features: new List<string>
+            {
+                "Op til 3 brugere",
+                "Online booking",
+                "Kalender & aftalestyring",
+                "Kundekartotek",
+                "SMS-påmindelser"
+            },
+            RequiresPayment: false,
+            IsContactSales: false
+        ),
+
+        ["pro"] = new PlanInfo(
+            Key: "pro",
+            Name: "Pro",
+            UserRange: "4-8 brugere",
+            PricePerMonth: 599,
+            BadgeText: "Mest populære",
+            BadgeClass: "popular",
+            BadgeIcon: "ph-star",
+            Features: new List<string>
+            {
+                "Op til 8 brugere",
+                "Alt fra Basis",
+                "Lagerstyring",
+                "Avancerede rapporter",
+                "Gavekort & klippekort",
+                "Prioriteret support"
+            },
+            RequiresPayment: true,
+            IsContactSales: false
+        ),
+
+        ["enterprise"] = new PlanInfo(
+            Key: "enterprise",
+            Name: "Enterprise",
+            UserRange: "8+ brugere",
+            PricePerMonth: null,
+            BadgeText: "Enterprise",
+            BadgeClass: "enterprise",
+            BadgeIcon: "ph-buildings",
+            Features: new List<string>
+            {
+                "Ubegrænset antal brugere",
+                "Alt fra Pro",
+                "Flere lokationer",
+                "Tilpasset integration",
+                "Dedikeret kontaktperson",
+                "SLA & uptime garanti"
+            },
+            RequiresPayment: false,
+            IsContactSales: true
+        )
+    };
+
+    public static PlanInfo GetPlan(string key)
+    {
+        if (Plans.TryGetValue(key.ToLowerInvariant(), out var plan))
+            return plan;
+
+        // Default to Pro if invalid key
+        return Plans["pro"];
+    }
+
+    public static IEnumerable<PlanInfo> GetAllPlans() => Plans.Values;
+
+    public static PlanInfo Basis => Plans["basis"];
+    public static PlanInfo Pro => Plans["pro"];
+    public static PlanInfo Enterprise => Plans["enterprise"];
+}