security: Add proper authentication, RBAC, and tenant isolation

- Add password hashing with bcrypt
- Add AuthService with proper login
- Add password strength validation
- Add RBAC middleware (AdminOnly, ManagerOrAdmin)
- Add tenant isolation middleware
- Update CRM handler with tenant filtering
- Add JWT fallback for development mode
- Add user context helpers
- Build successful

backend/middleware/context.go

@@ -0,0 +1,19 @@
+package middleware
+
+import "context"
+
+// contextKey är en privat typ för att undvika kollisioner
+ type contextKey int
+
+ const claimsKey contextKey = iota
+
+ // FromContext hämtar claims från context
+ func FromContext(ctx context.Context) (*Claims, bool) {
+ 	claims, ok := ctx.Value(claimsKey).(*Claims)
+ 	return claims, ok
+ }
+
+ // WithContext lägger till claims i context
+ func WithContext(ctx context.Context, claims *Claims) context.Context {
+ 	return context.WithValue(ctx, claimsKey, claims)
+ }