feat: implement Redis Streams support with stream checkpoints and update history

- Added Redis Streams operations to the message bus interface and implementation.
- Introduced StreamCheckpoint model to track last processed stream entry per document.
- Implemented UpsertStreamCheckpoint and GetStreamCheckpoint methods in the Postgres store.
- Created document_update_history table for storing update payloads for recovery and replay.
- Developed update persist worker to handle Redis Stream updates and persist them to Postgres.
- Enhanced Docker Compose configuration for Redis with persistence.
- Updated frontend API to support fetching document state with optional share token.
- Added connection stability monitoring in the Yjs document hook.

backend/internal/models/stream_checkpoint.go

@@ -0,0 +1,15 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// StreamCheckpoint tracks the last processed Redis Stream entry per document
+type StreamCheckpoint struct {
+	DocumentID   uuid.UUID `json:"document_id"`
+	LastStreamID string    `json:"last_stream_id"`
+	LastSeq      int64     `json:"last_seq"`
+	UpdatedAt    time.Time `json:"updated_at"`
+}