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

README.md

@@ -19,8 +19,8 @@ and expand to crowd-fund with time & money, then record and see the impact of co
 The migration is controlled by a **migration fence** that separates legacy Dexie code from the new SQLite implementation. See [Migration Fence Definition](doc/migration-fence-definition.md) for complete details.
 
 **Key Points**:
-- Legacy Dexie database is disabled by default (`USE_DEXIE_DB = false`)
-- All database operations go through `PlatformService`
+- Legacy Dexie database is disabled by default
+- All database operations go through `PlatformServiceMixin`
 - Migration tools provide controlled access to both databases
 - Clear separation between legacy and new code
 
@@ -100,7 +100,7 @@ The application uses a platform-agnostic database layer with Vue mixins for serv
 
 - Always use `PlatformServiceMixin` for database operations in components
 - Never import Dexie directly in application code
-- Test with `USE_DEXIE_DB = false` for new features
+- Test with PlatformServiceMixin for new features
 - Use migration tools for data transfer between systems
 - Leverage mixin's ultra-concise methods: `$db()`, `$exec()`, `$one()`, `$contacts()`, `$settings()`