feat: add channel message support and refactor UI components

- Implement `VkChannelMessage` domain and data models for channel message attachments
- Add `CHANNEL_MESSAGE` to `AttachmentType` and map it to relevant UI resources and strings
- Refactor `Sticker` and `Gift` composables to accept URL strings instead of domain objects for better decoupling
- Simplify `AppTheme` by removing redundant color animations and passing the color scheme directly to `MaterialExpressiveTheme`
- Update `LoginScreen` to include a theme toggle (classic vs. light) and improve back-button behavior by resetting error states
- Bump VK API version from 5.238 to 5.263
- Adjust layout and padding for sticker and gift attachment previews

feature/messageshistory/src/main/kotlin/dev/meloda/fast/messageshistory/presentation/attachments/Attachments.kt

@@ -119,12 +119,15 @@ fun Attachments(
 
                 AttachmentType.STICKER -> {
                     Sticker(
-                        item = attachment as VkStickerDomain
+                        url = (attachment as VkStickerDomain).getUrl(
+                            width = 256,
+                            withBackground = false
+                        )
                     )
                 }
 
                 AttachmentType.GIFT -> {
-                    Gift(item = attachment as VkGiftDomain)
+                    Gift(url = (attachment as VkGiftDomain).getDefaultThumbSizeOrLess())
                 }
 
                 AttachmentType.VIDEO_MESSAGE -> {

feature/messageshistory/src/main/kotlin/dev/meloda/fast/messageshistory/presentation/attachments/Gift.kt

@@ -21,25 +21,24 @@ import androidx.compose.ui.res.vectorResource
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import coil.compose.AsyncImage
-import dev.meloda.fast.model.api.domain.VkGiftDomain
 import dev.meloda.fast.ui.R
 
 @Composable
 fun Gift(
     modifier: Modifier = Modifier,
-    item: VkGiftDomain
+    url: String
 ) {
     Column(
-        modifier = modifier.width(192.dp),
+        modifier = modifier
+            .width(208.dp)
+            .padding(8.dp),
         verticalArrangement = Arrangement.spacedBy(4.dp)
     ) {
         AsyncImage(
-            model = item.getDefaultThumbSizeOrLess(),
+            model = url,
             contentDescription = null,
             contentScale = ContentScale.Crop,
-            modifier = Modifier
-                .padding(8.dp)
-                .fillMaxWidth()
+            modifier = Modifier.size(192.dp)
         )
 
         Row(

feature/messageshistory/src/main/kotlin/dev/meloda/fast/messageshistory/presentation/attachments/Sticker.kt

@@ -10,27 +10,23 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.unit.dp
 import coil.compose.AsyncImage
-import dev.meloda.fast.model.api.domain.VkStickerDomain
 
 @Composable
 fun Sticker(
     modifier: Modifier = Modifier,
-    item: VkStickerDomain
+    url: String?
 ) {
     Box(
-        modifier = modifier.size(192.dp),
+        modifier = modifier
+            .size(208.dp)
+            .padding(8.dp),
         contentAlignment = Alignment.Center
     ) {
         AsyncImage(
-            model = item.getUrl(
-                width = 256,
-                withBackground = false
-            ),
+            model = url,
             contentDescription = null,
             contentScale = ContentScale.Crop,
-            modifier = Modifier
-                .padding(8.dp)
-                .fillMaxSize()
+            modifier = Modifier.fillMaxSize()
         )
     }
 }