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/utils/logger.ts

@@ -11,6 +11,19 @@
 
 import { PlatformServiceFactory } from "@/services/PlatformServiceFactory";
 
+const _memoryLogs: string[] = [];
+
+export function appendToMemoryLogs(message: string): void {
+  _memoryLogs.push(`${new Date().toISOString()}: ${message}`);
+  if (_memoryLogs.length > 1000) {
+    _memoryLogs.splice(0, _memoryLogs.length - 1000);
+  }
+}
+
+export function getMemoryLogs(): string[] {
+  return [..._memoryLogs];
+}
+
 export function safeStringify(obj: unknown) {
   const seen = new WeakSet();