fix(types): fix TypeScript 6 compatibility in globals.d.ts

- Add 'declare module *.css {}' so CSS side-effect imports satisfy TS2882
- Make EasyButtonOptions.states optional to match upstream leaflet-easybutton
  types and fix TS2687 declaration-modifier mismatch

Author: techtimo

src/map-engine/globals.d.ts

@@ -55,7 +55,7 @@ declare global {
         }
 
         interface EasyButtonOptions {
-            states: EasyButtonState[];
+            states?: EasyButtonState[];
         }
 
         interface EasyButtonControl {
@@ -67,4 +67,6 @@ declare global {
     }
 }
 
+declare module '*.css' {}
+
 export {};