Finalize Dexie-to-SQLite migration prep: docs, circular dep removal, SQL helpers, tests

- Removed all vestigial Dexie/USE_DEXIE_DB references from code and docs
- Centralized DB logic in PlatformServiceMixin; resolved logger/databaseUtil circular dependency
- Modularized SQL helpers (`$generateInsertStatement`, `$generateUpdateStatement`) and added unit tests
- Created/updated migration tracking docs and helper script for cross-machine progress
- Confirmed all lint/type checks and tests pass; ready for systematic file migration

jest.config.js

@@ -0,0 +1,11 @@
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  moduleFileExtensions: ['ts', 'js', 'json', 'vue'],
+  transform: {
+    '^.+\\.ts$': 'ts-jest'
+  },
+  moduleNameMapper: {
+    '^@/(.*)$': '<rootDir>/src/$1'
+  }
+};