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

src/test/PlatformServiceMixinTest.vue

@@ -0,0 +1,42 @@
+<template>
+  <div>
+    <h2>PlatformServiceMixin Test</h2>
+    <button @click="testInsert">Test Insert</button>
+    <button @click="testUpdate">Test Update</button>
+    <pre>{{ result }}</pre>
+  </div>
+</template>
+
+<script lang="ts">
+import { Options, Vue } from "vue-facing-decorator";
+import { PlatformServiceMixin } from "@/utils/PlatformServiceMixin";
+
+@Options({
+  mixins: [PlatformServiceMixin],
+})
+export default class PlatformServiceMixinTest extends Vue {
+  result: string = "";
+
+  testInsert() {
+    const contact = {
+      name: "Alice",
+      age: 30,
+      isActive: true,
+      tags: ["friend"],
+    };
+    const { sql, params } = this.$generateInsertStatement(contact, "contacts");
+    this.result = `SQL: ${sql}\nParams: ${JSON.stringify(params)}`;
+  }
+
+  testUpdate() {
+    const changes = { name: "Bob", isActive: false };
+    const { sql, params } = this.$generateUpdateStatement(
+      changes,
+      "contacts",
+      "id = ?",
+      [42],
+    );
+    this.result = `SQL: ${sql}\nParams: ${JSON.stringify(params)}`;
+  }
+}
+</script>