ui: improve Compose stability and message UI

- Add minute/second abbreviations and kotlin.time-based relative time formatter
- Introduce FastPreview and update previews to use AppTheme with dark/dynamic colors
- Refactor attachments preview grid & waveform to use ImmutableList and reduce recompositions
- Tweak message bubble reply styling and swipe-to-reply animation/haptics
- Add Compose Stability Analyzer plugin and enable it in debug builds
- Cache shared images by sha256 and improve share intent/chooser text
- Minor UX polish (e.g., “No views”) and immutability annotations

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

@@ -1,7 +1,9 @@
 package dev.meloda.fast.model.api.domain
 
+import androidx.compose.runtime.Immutable
 import dev.meloda.fast.model.api.data.AttachmentType
 
+@Immutable
 interface VkAttachment {
     val type: AttachmentType
 }