Add startsWith parameter to getTopics method

Added optional startsWith parameter to topics query:
- Filters topics by prefix on the server side
- Updated TypeScript types
- Supports response with startsWith field

Version bumped to 0.7.5

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/offers.ts

@@ -143,11 +143,13 @@ export class RondevuOffers {
   async getTopics(options?: {
     limit?: number;
     offset?: number;
+    startsWith?: string;
   }): Promise<{
     topics: TopicInfo[];
     total: number;
     limit: number;
     offset: number;
+    startsWith?: string;
   }> {
     const params = new URLSearchParams();
 
@@ -159,6 +161,10 @@ export class RondevuOffers {
       params.set('offset', options.offset.toString());
     }
 
+    if (options?.startsWith) {
+      params.set('startsWith', options.startsWith);
+    }
+
     const url = `${this.baseUrl}/topics${
       params.toString() ? '?' + params.toString() : ''
     }`;