Adds support for filtering data during initial replication

.changeset/famous-cobras-give.md

@@ -0,0 +1,36 @@
+---
+"@powersync/service-sync-rules": minor
+"@powersync/service-core": minor
+"@powersync/service-module-postgres-storage": patch
+"@powersync/service-module-mysql": minor
+---
+
+Add snapshot_filter support for initial table replication
+
+Users can now configure snapshot filters in sync_rules.yaml to apply WHERE clauses during initial table snapshots. This reduces storage and bandwidth for large tables where only a subset of rows match sync rules.
+
+Features:
+- Configure global filters for initial replication
+- CDC changes continue to work normally, only affecting rows in storage
+- Supports MySQL source with PostgreSQL storage 
+
+Example:
+```yaml
+# EXPLICIT: "I only want data from the last 90 days, period"
+initial_snapshot_filters:
+  orders:
+    sql: "created_at > DATE_SUB(NOW(), INTERVAL 90 DAY)"
+
+  logs:
+    sql: "timestamp > NOW() - INTERVAL '7 days'"
+
+bucket_definitions:
+  # This works - queries recent orders
+  recent_orders:
+    data:
+      - SELECT * FROM orders WHERE created_at > DATE_SUB(NOW(), INTERVAL 30 DAY)
+
+  # This will be EMPTY initially - and that's OK for logs
+  all_logs:
+    data:
+      - SELECT * FROM logs