feat: initial DataMigration extension for case data backup/restore

Full case data migration tool with 3 console commands:
- data-migration-export: exports all case-related entities (27 types) + files
- data-migration-import: restores backup to target DB with dry-run support
- data-migration-status: shows entity counts from live DB or backup

Supports preserve-ids, skip-duplicates, batch processing, and attachment
file copying. Imports with hooks disabled to prevent side effects.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

build.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+# Build extension ZIP package
+set -euo pipefail
+VERSION=$(python3 -c "import json; print(json.load(open('manifest.json'))['version'])")
+MODULE=$(python3 -c "import json; m=json.load(open('manifest.json')); print(m.get('module', m['name']))")
+ZIPNAME="${MODULE}-${VERSION}.zip"
+
+# Update version in README.md if it exists
+if [[ -f README.md ]]; then
+  sed -i "s/\*\*גרסה:\*\* [^ |]*/\*\*גרסה:\*\* ${VERSION}/" README.md
+fi
+echo "Building $ZIPNAME..."
+rm -f "$ZIPNAME"
+zip -r "$ZIPNAME" manifest.json files/ scripts/ \
+  -x "*.DS_Store" "*__MACOSX*" "*.zip" 2>/dev/null || \
+zip -r "$ZIPNAME" manifest.json files/ \
+  -x "*.DS_Store" "*__MACOSX*" "*.zip"
+echo "✓ Built: $ZIPNAME ($(du -h "$ZIPNAME" | cut -f1))"