feat(mesh-ui): attach button + ContentRef card in chat

Compose row gains a 📎 attach button that uploads the file via /api/blob
and calls mesh.send-content for the selected peer. Received content_ref
bubbles render as a caption+filename card with either an inline image
preview or a Download button that calls mesh.fetch-content and swaps in
the returned local_url.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/src/stores/mesh.ts

@@ -47,6 +47,7 @@ export type MeshMessageTypeLabel =
   | 'tx_confirmation'
   | 'lightning_relay'
   | 'lightning_relay_response'
+  | 'content_ref'
 
 export interface MeshMessage {
   id: number
@@ -375,6 +376,38 @@ export const useMeshStore = defineStore('mesh', () => {
     }
   }
 
+  async function sendContent(contactId: number, cid: string, caption?: string) {
+    try {
+      sending.value = true
+      error.value = null
+      const res = await rpcClient.call<{ sent: boolean; message_id: number; cid: string; size: number }>({
+        method: 'mesh.send-content',
+        params: { contact_id: contactId, cid, caption },
+      })
+      if (res.sent) await fetchMessages()
+      return res
+    } catch (err: unknown) {
+      error.value = err instanceof Error ? err.message : 'Failed to send content'
+      throw err
+    } finally {
+      sending.value = false
+    }
+  }
+
+  async function fetchContent(params: {
+    cid: string
+    sender_onion: string
+    cap_token: string
+    cap_exp: number
+    mime?: string
+    filename?: string
+  }) {
+    return rpcClient.call<{ fetched: boolean; cached: boolean; cid: string; size?: number; mime?: string }>({
+      method: 'mesh.fetch-content',
+      params,
+    })
+  }
+
   async function getSessionStatus(contactId: number): Promise<SessionStatus> {
     return rpcClient.call<SessionStatus>({
       method: 'mesh.session-status',
@@ -495,6 +528,8 @@ export const useMeshStore = defineStore('mesh', () => {
     sendInvoice,
     sendCoordinate,
     sendAlert,
+    sendContent,
+    fetchContent,
     getSessionStatus,
     rotatePrekeys,
     getNodePositions,