Mobile notifications for iOS (#210)

* mobile: wire notification registration and listener

* implement backend components for push notifications

* refactor: agentic comment cleanup

* docs: use proper module name for particle processor

* set required env variables for push notifications

* bump version

* fix: always upsert push token on mobile start

* Revert "fix: always upsert push token on mobile start"

This reverts commit 90ff18a788.

* send push notifications regardless of online status

go/internal/pusher/hub.go

@@ -43,7 +43,6 @@ type Hub struct {
 	remoteEventCh chan *remoteEvent
 }
 
-// NewHub creates a new Hub.
 func NewHub(bridge *RedisBridge, authorizer *Authorizer) *Hub {
 	return &Hub{
 		channels:      make(map[string]*Channel),
@@ -84,7 +83,6 @@ func (h *Hub) Run(ctx context.Context) {
 }
 
 func (h *Hub) handleSubscribe(ctx context.Context, req *subscribeRequest) {
-	// Authorize channel access
 	if err := h.authorizer.Authorize(ctx, req.channelID, req.conn.humanID); err != nil {
 		req.conn.Send(ServerMessage{
 			Type:    TypeError,
@@ -94,7 +92,6 @@ func (h *Hub) handleSubscribe(ctx context.Context, req *subscribeRequest) {
 		return
 	}
 
-	// Get or create local channel
 	ch, ok := h.channels[req.channelID]
 	if !ok {
 		ch = newChannel(req.channelID)
@@ -104,32 +101,27 @@ func (h *Hub) handleSubscribe(ctx context.Context, req *subscribeRequest) {
 	// Capture before addMember so multi-tab joins don't emit a spurious join.
 	wasPresentLocally := ch.hasHumanID(req.conn.humanID)
 
-	// Add to local channel
 	ch.addMember(req.conn, req.conn.humanID)
 
-	// Track in reverse index
 	if h.connChannels[req.conn] == nil {
 		h.connChannels[req.conn] = make(map[string]bool)
 	}
 	h.connChannels[req.conn][req.channelID] = true
 
-	// Register in Redis and get global presence
 	presence, err := h.bridge.Subscribe(ctx, req.channelID, req.conn.id, req.conn.humanID)
 	if err != nil {
 		slog.Error("redis subscribe failed", "channelId", req.channelID, "error", err)
-		// Still send local presence as fallback
+		// Fall back to local-only presence.
 		presence = ch.localHumanIDs()
 	}
 
-	// Send subscribed ack with presence snapshot
 	req.conn.Send(ServerMessage{
 		Type:     TypeSubscribed,
 		Channel:  req.channelID,
 		Presence: presence,
 	})
 
-	// Notify other local members. The Redis self-filter drops our own echo,
-	// so same-pod peers would otherwise never hear about this join.
+	// Redis self-filter drops our own echo, so same-pod peers need a direct nudge.
 	if !wasPresentLocally {
 		ch.broadcast(ServerMessage{
 			Type:    TypeJoin,
@@ -147,18 +139,15 @@ func (h *Hub) handleUnsubscribe(ctx context.Context, req *unsubscribeRequest) {
 
 	ch.removeMember(req.conn)
 
-	// Remove from reverse index
 	if chans, ok := h.connChannels[req.conn]; ok {
 		delete(chans, req.channelID)
 	}
 
-	// Update Redis
 	if err := h.bridge.Unsubscribe(ctx, req.channelID, req.conn.id, req.conn.humanID); err != nil {
 		slog.Error("redis unsubscribe failed", "channelId", req.channelID, "error", err)
 	}
 
-	// Notify other local members iff the humanID is fully gone from this pod
-	// (multi-tab: other conns keep them present, so no leave fires).
+	// Only emit leave once the humanID has no remaining tabs on this pod.
 	if !ch.hasHumanID(req.conn.humanID) {
 		ch.broadcast(ServerMessage{
 			Type:    TypeLeave,
@@ -167,7 +156,6 @@ func (h *Hub) handleUnsubscribe(ctx context.Context, req *unsubscribeRequest) {
 		}, req.conn)
 	}
 
-	// Clean up empty local channel
 	if ch.isEmpty() {
 		delete(h.channels, req.channelID)
 	}
@@ -179,13 +167,12 @@ func (h *Hub) handleBroadcast(ctx context.Context, req *broadcastRequest) {
 		return
 	}
 
-	// Check that the sender is actually in the channel
 	if _, isMember := ch.members[req.conn]; !isMember {
 		req.conn.sendError("not subscribed to channel: " + req.channelID)
 		return
 	}
 
-	// Deliver to local connections (except sender)
+	// Local fanout (excluding sender), then publish for other pods.
 	ch.broadcast(ServerMessage{
 		Type:    TypeMessage,
 		Channel: req.channelID,
@@ -193,7 +180,6 @@ func (h *Hub) handleBroadcast(ctx context.Context, req *broadcastRequest) {
 		Payload: req.payload,
 	}, req.conn)
 
-	// Publish to Redis for other pods
 	h.bridge.Broadcast(ctx, req.channelID, req.conn.humanID, req.payload)
 }
 
@@ -234,7 +220,8 @@ func (h *Hub) handleDisconnect(ctx context.Context, conn *Conn) {
 func (h *Hub) handleRemoteEvent(evt *remoteEvent) {
 	ch, ok := h.channels[evt.channelID]
 	if !ok {
-		return // no local connections care about this channel
+		// No local subscribers — drop the event.
+		return
 	}
 
 	switch evt.event.Type {
@@ -262,12 +249,10 @@ func (h *Hub) handleRemoteEvent(evt *remoteEvent) {
 	}
 }
 
-// Subscribe enqueues a subscribe request for the given connection and channel.
 func (h *Hub) Subscribe(conn *Conn, channelID string) {
 	h.subscribeCh <- &subscribeRequest{conn: conn, channelID: channelID}
 }
 
-// disconnect sends a connection to the disconnect channel.
 func (h *Hub) disconnect(conn *Conn) {
 	h.disconnectCh <- conn
 }