fix(params): enforce non-undefined route parameter values

- Update `Params` type to disallow `undefined` values for clarity.
- Default route parameter values to empty strings if `null` or `undefined`.

Signed-off-by: Max P. <Mail@MPassarello.de>

src/Types/Params.ts

@@ -7,4 +7,4 @@
  * All values are strings and should be considered read-only, as they are
  * extracted by the router and should not be modified by application code.
  */
-export type Params = Record<string, string | undefined>;
+export type Params = Record<string, string>;

src/Utils/createRouteMatcher.ts

@@ -35,7 +35,7 @@ export function createRouteMatcher(
         // 3b. Extract route params
         const params: Params = {};
         for (const [key, value] of Object.entries(result.pathname.groups)) {
-            params[key] = value;
+            params[key] = value ?? ''; // null → empty string
         }
 
         // 3c. Extract query parameters – keep duplicates as arrays