feat(server): auto index all workspaces to indexer (#12205)

close CLOUD-207

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Introduced automated periodic indexing of workspaces with a new job type and a scheduled cron job running every 30 seconds.
  - Added a unique sequential identifier (`sid`) and an "indexed" flag to workspaces to track indexing status.
- **Improvements**
  - Enhanced workspace indexing to handle missing workspaces and snapshots distinctly and selectively index documents.
  - Added ability to query workspaces after a given identifier with result limits.
- **Bug Fixes**
  - Improved error handling and logging during workspace indexing operations.
- **Tests**
  - Expanded test coverage for workspace indexing and auto-indexing, including scheduling and edge cases.
- **Chores**
  - Updated data models and schema to support new workspace fields and indexing features.
  - Enhanced mock data utilities to allow custom timestamps.
  - Improved type safety and flexibility in document snapshot retrieval.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/migrations/20250509070728_add_workspace_sid_and_indexed/migration.sql

@@ -0,0 +1,14 @@
+/*
+  Warnings:
+
+  - A unique constraint covering the columns `[sid]` on the table `workspaces` will be added. If there are existing duplicate values, this will fail.
+
+*/
+-- AlterTable
+ALTER TABLE "workspaces" ADD COLUMN "sid" INT GENERATED BY DEFAULT AS IDENTITY;
+
+-- CreateIndex
+CREATE UNIQUE INDEX "workspaces_sid_key" ON "workspaces"("sid");
+
+-- AlterTable
+ALTER TABLE "workspaces" ADD COLUMN     "indexed" BOOLEAN NOT NULL DEFAULT false;