feat: replace payment modals with page-based navigation

- Add /balance/top-up route for payment method selection
- Add /balance/top-up/:methodId route for amount entry and payment
- Remove TopUpModal component (619 lines)
- Simplify InsufficientBalancePrompt to use navigate instead of modals
- Support ?amount and ?returnTo query params for cross-page data flow
- Fix nav isActive to highlight Balance on sub-routes
- Remove unused MainButton platform abstraction
- Increase toast accent opacity for better visibility

src/platform/hooks/useMainButton.ts

@@ -1,111 +0,0 @@
-import { useEffect, useRef, useCallback } from 'react';
-import { usePlatform } from '@/platform/hooks/usePlatform';
-import type { MainButtonConfig } from '@/platform/types';
-
-interface UseMainButtonOptions extends Omit<MainButtonConfig, 'onClick'> {
-  /**
-   * Whether the main button should be visible
-   * @default true
-   */
-  visible?: boolean;
-}
-
-/**
- * Hook to manage the Telegram MainButton
- * Automatically shows/hides based on component lifecycle
- *
- * @param onClick - Callback when main button is pressed
- * @param options - Configuration options
- *
- * @example
- * ```tsx
- * function SubmitForm() {
- *   const mutation = useMutation(...);
- *
- *   useMainButton(handleSubmit, {
- *     text: t('actions.submit'),
- *     isLoading: mutation.isPending,
- *     isActive: isFormValid,
- *   });
- * }
- * ```
- */
-export function useMainButton(
-  onClick: (() => void) | null | undefined,
-  options: UseMainButtonOptions = { text: '' },
-): void {
-  const { mainButton, capabilities } = usePlatform();
-  const { visible = true, text, isLoading, isActive, color, textColor } = options;
-
-  // Use ref to prevent callback recreation issues
-  const callbackRef = useRef(onClick);
-  callbackRef.current = onClick;
-
-  // Stable callback wrapper
-  const handleClick = useCallback(() => {
-    callbackRef.current?.();
-  }, []);
-
-  useEffect(() => {
-    // If no native main button support, do nothing
-    // UI components will render their own submit buttons
-    if (!capabilities.hasMainButton) {
-      return;
-    }
-
-    // If callback is null/undefined or visible is false, hide button
-    if (!onClick || !visible || !text) {
-      mainButton.hide();
-      return;
-    }
-
-    // Show the main button with configuration
-    mainButton.show({
-      text,
-      onClick: handleClick,
-      isLoading,
-      isActive,
-      color,
-      textColor,
-    });
-
-    // Cleanup: hide button when component unmounts
-    return () => {
-      mainButton.hide();
-    };
-  }, [
-    mainButton,
-    capabilities.hasMainButton,
-    handleClick,
-    onClick,
-    visible,
-    text,
-    isLoading,
-    isActive,
-    color,
-    textColor,
-  ]);
-}
-
-/**
- * Hook for simple main button usage
- * Shows button only when conditions are met
- *
- * @param text - Button text
- * @param onClick - Click handler
- * @param enabled - Whether button should be shown and active
- * @param loading - Whether to show loading state
- */
-export function useSimpleMainButton(
-  text: string,
-  onClick: () => void,
-  enabled: boolean = true,
-  loading: boolean = false,
-): void {
-  useMainButton(enabled ? onClick : null, {
-    text,
-    isLoading: loading,
-    isActive: enabled && !loading,
-    visible: enabled,
-  });
-}