chore(app): lint cleanups (const constructors, local function)

lib/components/lightning.dart

@@ -182,7 +182,7 @@ class _LightningPainter extends CustomPainter {
 
   @override
   void paint(Canvas canvas, Size size) {
-    final toScreen = (Offset p) => Offset(p.dx * size.width, p.dy * size.height);
+    Offset toScreen(Offset p) => Offset(p.dx * size.width, p.dy * size.height);
     final scaledMain = bolt.mainPath.map(toScreen).toList();
     final scaledBranches = bolt.branches
         .map((b) => b.map(toScreen).toList())

lib/components/sidebar_contents/discord_link_button.dart

@@ -14,8 +14,8 @@ class DiscordLinkButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return IconButton(
-      icon: const Icon(Icons.discord, color: AppColors.textWhite, size: 28),
+    return const IconButton(
+      icon: Icon(Icons.discord, color: AppColors.textWhite, size: 28),
       onPressed: launchDiscord,
       tooltip: 'Join Discord',
       splashRadius: 24,

lib/components/sidebar_contents/gdpr_button.dart

@@ -76,8 +76,8 @@ class GdprButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return IconButton(
-      icon: const Icon(Icons.admin_panel_settings_outlined,
+    return const IconButton(
+      icon: Icon(Icons.admin_panel_settings_outlined,
           color: AppColors.textWhite, size: 28),
       onPressed: showConsentForm,
       tooltip: 'Ad consent & privacy choices',

lib/components/sidebar_contents/info_button.dart

@@ -14,8 +14,8 @@ class InfoButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return IconButton(
-      icon: const Icon(Icons.help_outline, color: AppColors.textWhite, size: 28),
+    return const IconButton(
+      icon: Icon(Icons.help_outline, color: AppColors.textWhite, size: 28),
       onPressed: launchGitHub,
       tooltip: 'About ReVoltVPN',
       splashRadius: 24,

lib/components/sidebar_contents/privacy_policy_button.dart

@@ -14,8 +14,8 @@ class PrivacyPolicyButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return IconButton(
-      icon: const Icon(Icons.privacy_tip_outlined, color: AppColors.textWhite, size: 28),
+    return const IconButton(
+      icon: Icon(Icons.privacy_tip_outlined, color: AppColors.textWhite, size: 28),
       onPressed: launchPrivacyPolicy,
       tooltip: 'Privacy Policy',
       splashRadius: 24,

lib/components/sidebar_contents/website_button.dart

@@ -14,8 +14,8 @@ class WebsiteButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return IconButton(
-      icon: const Icon(Icons.language, color: AppColors.textWhite, size: 28),
+    return const IconButton(
+      icon: Icon(Icons.language, color: AppColors.textWhite, size: 28),
       onPressed: launchWebsite,
       tooltip: 'Website',
       splashRadius: 24,

lib/logic/updater.dart

@@ -189,7 +189,7 @@ class Updater {
     }
 
     try {
-      final result = await MethodChannel('com.revoltvpn.app/installer')
+      final result = await const MethodChannel('com.revoltvpn.app/installer')
           .invokeMethod<String>('getInstallerPackage');
       _cachedSource = (result == 'com.android.vending')
           ? InstallSource.playStore