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/store/stream_checkpoint.go

@@ -0,0 +1,46 @@
+package store
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/M1ngdaXie/realtime-collab/internal/models"
+	"github.com/google/uuid"
+)
+
+// UpsertStreamCheckpoint creates or updates the stream checkpoint for a document
+func (s *PostgresStore) UpsertStreamCheckpoint(ctx context.Context, documentID uuid.UUID, streamID string, seq int64) error {
+	query := `
+		INSERT INTO stream_checkpoints (document_id, last_stream_id, last_seq, updated_at)
+		VALUES ($1, $2, $3, NOW())
+		ON CONFLICT (document_id)
+		DO UPDATE SET last_stream_id = EXCLUDED.last_stream_id,
+		             last_seq = EXCLUDED.last_seq,
+		             updated_at = NOW()
+	`
+
+	if _, err := s.db.ExecContext(ctx, query, documentID, streamID, seq); err != nil {
+		return fmt.Errorf("failed to upsert stream checkpoint: %w", err)
+	}
+	return nil
+}
+
+// GetStreamCheckpoint retrieves the stream checkpoint for a document
+func (s *PostgresStore) GetStreamCheckpoint(ctx context.Context, documentID uuid.UUID) (*models.StreamCheckpoint, error) {
+	query := `
+		SELECT document_id, last_stream_id, last_seq, updated_at
+		FROM stream_checkpoints
+		WHERE document_id = $1
+	`
+
+	var checkpoint models.StreamCheckpoint
+	if err := s.db.QueryRowContext(ctx, query, documentID).Scan(
+		&checkpoint.DocumentID,
+		&checkpoint.LastStreamID,
+		&checkpoint.LastSeq,
+		&checkpoint.UpdatedAt,
+	); err != nil {
+		return nil, fmt.Errorf("failed to get stream checkpoint: %w", err)
+	}
+	return &checkpoint, nil
+}