feat: message reactions + link/image previews

Reactions (full stack):
- Wire: MsgReaction peer message (reaction_mid, reaction_emoji)
- Store: reactions table (mid, emoji, from_peer), SaveReaction, ReactionsForRoom
- Daemon: CmdSendReaction IPC command; EvtReaction IPC event; stored reactions
  replayed to newly-connected IPC clients alongside history
- Web UI: reactions state (mid → emoji → [fromId]); hover a message to reveal
  a + button; click opens a 6-emoji picker (👍❤️😂😮😢🙏); reaction chips
  appear below the message with count and tooltip; own reactions highlighted

Link/image previews:
- URLs in message text rendered as clickable <a> links
- Image URLs (.jpg/.jpeg/.png/.gif/.webp/blob:/data:image) rendered as inline
  thumbnails (max 320×200px) below the link

Also scoped push notifications architecture in FUTURE.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/store/index.ts

@@ -58,6 +58,8 @@ interface WasteState {
   fileProgress: Record<string, { peerId: string; name: string; received: number; total: number }>
   // partial downloads found on daemon startup: sha256 → info
   resumableFiles: Record<string, { name: string; from: string; size: number; offset: number }>
+  // reactions: mid → emoji → [fromId, ...]
+  reactions: Record<string, Record<string, string[]>>
 
   // actions
   connect: (url: string) => void
@@ -74,6 +76,7 @@ interface WasteState {
   rejectOffer: (peerId: string, xid: string) => void
   cancelTransfer: (peerId: string, xid: string, direction: 'recv' | 'send') => void
   createRoom: (name: string) => void
+  sendReaction: (networkId: string, mid: string, emoji: string) => void
   logout: (clearIdentity: boolean) => void
   handleEvent: (msg: IpcMessage) => void
 }
@@ -101,6 +104,7 @@ export const useWaste = create<WasteState>((set, get) => ({
   pendingOffers: {},
   fileProgress: {},
   resumableFiles: {},
+  reactions: {},
 
   connect(url: string) {
     const adapter = new DaemonAdapter(url)
@@ -189,6 +193,10 @@ export const useWaste = create<WasteState>((set, get) => ({
     window.location.reload()
   },
 
+  sendReaction(networkId, mid, emoji) {
+    get().send({ type: 'send_reaction', network_id: networkId, reaction_mid: mid, reaction_emoji: emoji })
+  },
+
   createRoom(name) {
     const netId = get().activeNetworkId
     if (!netId || !name.trim()) return
@@ -374,6 +382,19 @@ export const useWaste = create<WasteState>((set, get) => ({
         set(s => ({ resumableFiles: { ...s.resumableFiles, ...byHash } }))
         break
       }
+      case 'reaction': {
+        const mid = msg.reaction_mid
+        const emoji = msg.reaction_emoji
+        const from = msg.peer_id
+        if (!mid || !emoji || !from) break
+        set(s => {
+          const byEmoji = { ...(s.reactions[mid] ?? {}) }
+          const existing = byEmoji[emoji] ?? []
+          if (existing.includes(from)) return s
+          return { reactions: { ...s.reactions, [mid]: { ...byEmoji, [emoji]: [...existing, from] } } }
+        })
+        break
+      }
       case 'history_loaded': {
         const room = msg.room
         const incoming = (msg.messages ?? []) as ChatMessage[]