Media attachment cards with popover players and shared volume

- Audio/video attachments render as media cards (cover or icon,
  title/artist/size) instead of plain file chips; image attachments
  use 3:2 thumbnails matching the audio card height
- Players open in a Popover (autoplay on open) with a dimming
  overlay; AudioPlayerDialog/VideoPlayerDialog removed
- New useMediaVolume composable shares volume/mute between all
  audio players and Plyr via the 4brett-player storage key
- Player buttons and Plyr controls follow the theme border radius
- Portrait videos: aspect is applied even when metadata loaded
  before hydration, and the raw video is height-capped pre-JS

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/composables/useMediaVolume.ts

@@ -0,0 +1,51 @@
+import { useMediaControls } from '@vueuse/core'
+
+// Derselbe localStorage-Key wie Plyr im VideoPlayer — so teilen sich Video- und
+// Audio-Player eine gemerkte Lautstärke (in beide Richtungen)
+const STORAGE_KEY = '4brett-player'
+
+interface StoredPrefs {
+  volume?: number
+  muted?: boolean
+}
+
+function readPrefs(): StoredPrefs {
+  try {
+    const raw = localStorage.getItem(STORAGE_KEY)
+    return raw ? JSON.parse(raw) as StoredPrefs : {}
+  }
+  catch {
+    return {}
+  }
+}
+
+export function useMediaVolume(target: Parameters<typeof useMediaControls>[0]) {
+  const controls = useMediaControls(target)
+
+  if (import.meta.client) {
+    const applyStored = () => {
+      const prefs = readPrefs()
+      if (typeof prefs.volume === 'number' && controls.volume.value !== prefs.volume) {
+        controls.volume.value = prefs.volume
+      }
+      if (typeof prefs.muted === 'boolean' && controls.muted.value !== prefs.muted) {
+        controls.muted.value = prefs.muted
+      }
+    }
+
+    watch(toRef(target), (el) => {
+      if (el) applyStored()
+    }, { immediate: true })
+
+    watch([controls.volume, controls.muted], ([v, m]) => {
+      const prefs = readPrefs()
+      if (prefs.volume === v && prefs.muted === m) return
+      try {
+        localStorage.setItem(STORAGE_KEY, JSON.stringify({ ...prefs, volume: v, muted: m }))
+      }
+      catch { /* Storage deaktiviert/voll */ }
+    })
+  }
+
+  return controls
+}