refactor: migrate to eslint flat config and format codebase with prettier

- Remove legacy .eslintrc.cjs and .eslintignore
- Add eslint.config.js with flat config, security rules (no-eval, no-implied-eval, no-new-func, no-script-url)
- Add .prettierrc and .prettierignore
- Format entire codebase with prettier

src/api/miniapp.ts

@@ -1,22 +1,22 @@
-import axios, { AxiosError } from 'axios'
+import axios, { AxiosError } from 'axios';
 
 export interface MiniappCreatePaymentPayload {
-  initData: string
-  method: string
-  amountKopeks?: number | null
-  option?: string | null
+  initData: string;
+  method: string;
+  amountKopeks?: number | null;
+  option?: string | null;
 }
 
 export interface MiniappCreatePaymentResponse {
-  payment_url: string
-  amount_kopeks?: number
-  extra?: Record<string, unknown>
+  payment_url: string;
+  amount_kopeks?: number;
+  extra?: Record<string, unknown>;
 }
 
 export const miniappApi = {
   // Create payment inside Telegram Mini App (same flow as miniapp/index.html)
   createPayment: async (
-    payload: MiniappCreatePaymentPayload
+    payload: MiniappCreatePaymentPayload,
   ): Promise<MiniappCreatePaymentResponse> => {
     try {
       const response = await axios.post<MiniappCreatePaymentResponse>(
@@ -29,15 +29,16 @@ export const miniappApi = {
         },
         {
           headers: { 'Content-Type': 'application/json' },
-        }
-      )
-      return response.data
+        },
+      );
+      return response.data;
     } catch (error) {
-      const axiosError = error as AxiosError<{ detail?: string; message?: string }>
-      const message = axiosError.response?.data?.detail
-        || axiosError.response?.data?.message
-        || 'Failed to create payment'
-      throw new Error(message)
+      const axiosError = error as AxiosError<{ detail?: string; message?: string }>;
+      const message =
+        axiosError.response?.data?.detail ||
+        axiosError.response?.data?.message ||
+        'Failed to create payment';
+      throw new Error(message);
     }
   },
-}
+};