feat(canvas): native field preservation, label materialization, batch workspace delete (#12)

* feat(canvas): native field preservation, label materialization, batch workspace delete

- fillNativeFields() + repairContainerBinding() in db layer ensure every
  element stored in SQLite is a complete, round-trippable Excalidraw element
  with correct containerId ↔ boundElements bidirectional binding
- materializeLabel() in server.ts: shapes with label.text/text produce a
  native bound text element at write time (create, update, batch) so text
  follows its container when moved — matches VSCode Excalidraw extension behavior
- Batch workspace UI: Select/Unselect All, per-row checkboxes, Delete N
  workspaces button with confirmation
- POST /api/tenants/batch-delete: delete up to 50 tenants in one request
- 42 new backend tests; 519 total passing
- Bump version 1.0.6 → 1.1.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(tests): update e2e assertions for label materialization

phase2-regressions: label is now a native bound text element
(id: pos-stable-1-label) — check bound text element text instead
of container.label?.text which is no longer stored.

sync-flows FTS: search now matches the bound text element (fts-el-label)
rather than the container — accept either id as valid match.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "excalidraw-mcp-sentinel",
-  "version": "1.0.3",
+  "version": "1.1.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "excalidraw-mcp-sentinel",
-      "version": "1.0.3",
+      "version": "1.1.0",
       "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {