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

build.gradle.kts

@@ -9,4 +9,5 @@ plugins {
     alias(libs.plugins.ksp) apply false
     alias(libs.plugins.module.graph) apply true
     alias(libs.plugins.versions) apply true
+    alias(libs.plugins.stability.analyzer) apply false
 }