feat: Add admin calendar and improve availability management

- Add admin calendar component with booking overview and status management
- Implement treatment-specific availability slots with automatic duration
- Enhance availability management with better UI and error handling
- Move admin credentials to .env configuration
- Add .env.example with all required environment variables
- Update README.md with comprehensive setup guide including PowerShell password hash generation
- Improve slot deletion with proper error handling and user feedback
- Add toast notifications for better UX

scripts/start-with-email.ps1

@@ -1,20 +1,22 @@
 $ErrorActionPreference = "Stop"
 
-param(
-  [Parameter(Mandatory = $true)]
-  [string]$ResendApiKey,
-
-  [Parameter(Mandatory = $false)]
-  [string]$EmailFrom = "Stargirlnails <no-reply@stargirlnails.de>",
-
-  [Parameter(Mandatory = $false)]
-  [string]$AdminEmail
-)
-
-Write-Host "Setting environment variables for Resend..."
-$env:RESEND_API_KEY = $ResendApiKey
-$env:EMAIL_FROM = $EmailFrom
-if ($AdminEmail) { $env:ADMIN_EMAIL = $AdminEmail }
+# Lade .env Datei automatisch
+Write-Host "Loading .env file..."
+if (Test-Path ".env") {
+    Get-Content ".env" | ForEach-Object {
+        if ($_ -match '^([^#][^=]+)=(.*)$') {
+            $name = $matches[1].Trim()
+            $value = $matches[2].Trim()
+            [Environment]::SetEnvironmentVariable($name, $value, 'Process')
+            Write-Host "✓ Loaded from .env: $name" -ForegroundColor Green
+        }
+    }
+    Write-Host "Environment variables loaded from .env file" -ForegroundColor Cyan
+} else {
+    Write-Warning ".env file not found!"
+    Write-Host "Please create a .env file with your environment variables." -ForegroundColor Red
+    exit 1
+}
 
 Write-Host "Starting app with pnpm dev..."
 pnpm dev