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

core/model/src/main/kotlin/dev/meloda/fast/model/api/data/AttachmentType.kt

@@ -30,7 +30,8 @@ enum class AttachmentType(var value: String) {
     ARTICLE("article"),
     VIDEO_MESSAGE("video_message"),
     GROUP_CHAT_STICKER("ugc_sticker"),
-    STICKER_PACK_PREVIEW("sticker_pack_preview")
+    STICKER_PACK_PREVIEW("sticker_pack_preview"),
+    CHANNEL_MESSAGE("channel_message")
     ;
 
     fun isMultiple(): Boolean = this in listOf(PHOTO, VIDEO, AUDIO, FILE)

core/model/src/main/kotlin/dev/meloda/fast/model/api/data/VkAttachmentItemData.kt

@@ -35,7 +35,8 @@ data class VkAttachmentItemData(
     @Json(name = "article") val article: VkArticleData?,
     @Json(name = "video_message") val videoMessage: VkVideoMessageData?,
     @Json(name = "ugc_sticker") val groupSticker: VkGroupStickerData?,
-    @Json(name = "sticker_pack_preview") val stickerPackPreview: VkStickerPackPreviewData?
+    @Json(name = "sticker_pack_preview") val stickerPackPreview: VkStickerPackPreviewData?,
+    @Json(name = "channel_message") val channelMessageData: VkChannelMessageData?
 ) {
     fun toDomain(): VkAttachment = when (AttachmentType.parse(type)) {
         AttachmentType.UNKNOWN -> VkUnknownAttachment
@@ -66,5 +67,6 @@ data class VkAttachmentItemData(
         AttachmentType.VIDEO_MESSAGE -> videoMessage?.toDomain()
         AttachmentType.GROUP_CHAT_STICKER -> groupSticker?.toDomain()
         AttachmentType.STICKER_PACK_PREVIEW -> stickerPackPreview?.toDomain()
+        AttachmentType.CHANNEL_MESSAGE -> channelMessageData?.toDomain()
     } ?: VkUnknownAttachment
 }

core/model/src/main/kotlin/dev/meloda/fast/model/api/data/VkChannelMessageData.kt

@@ -0,0 +1,40 @@
+package dev.meloda.fast.model.api.data
+
+import com.squareup.moshi.Json
+import com.squareup.moshi.JsonClass
+import dev.meloda.fast.model.api.domain.VkChannelMessage
+
+@JsonClass(generateAdapter = true)
+data class VkChannelMessageData(
+    @Json(name = "channel_id") val channelId: Long,
+    @Json(name = "cmid") val cmId: Long,
+    @Json(name = "author_id") val authorId: Long,
+    @Json(name = "channel_info") val channelInfo: ChannelInfo,
+    @Json(name = "channel_type") val channelType: String,
+    @Json(name = "guid") val guid: String,
+    @Json(name = "text") val text: String?,
+    @Json(name = "time") val time: Long,
+    @Json(name = "attachments") val attachments: List<VkAttachmentItemData> = emptyList(),
+) : VkAttachmentData {
+
+    @JsonClass(generateAdapter = true)
+    data class ChannelInfo(
+        @Json(name = "photo_base") val photoBase: String?,
+        @Json(name = "title") val title: String
+    )
+
+    fun toDomain(): VkChannelMessage = VkChannelMessage(
+        channelId = channelId,
+        cmId = cmId,
+        authorId = authorId,
+        channelInfo = VkChannelMessage.ChannelInfo(
+            title = channelInfo.title,
+            photoBase = channelInfo.photoBase
+        ),
+        channelType = channelType,
+        guid = guid,
+        text = text,
+        time = time,
+        attachments = attachments.map(VkAttachmentItemData::toDomain),
+    )
+}

core/model/src/main/kotlin/dev/meloda/fast/model/api/domain/VkChannelMessage.kt

@@ -0,0 +1,23 @@
+package dev.meloda.fast.model.api.domain
+
+import dev.meloda.fast.model.api.data.AttachmentType
+
+data class VkChannelMessage(
+    val channelId: Long,
+    val cmId: Long,
+    val authorId: Long,
+    val channelInfo: ChannelInfo,
+    val channelType: String,
+    val guid: String,
+    val text: String?,
+    val time: Long,
+    val attachments: List<VkAttachment>?,
+) : VkAttachment {
+
+    data class ChannelInfo(
+        val title: String,
+        val photoBase: String?
+    )
+
+    override val type: AttachmentType = AttachmentType.CHANNEL_MESSAGE
+}