refactor(config): centralize app config in Dexie

Migrates scattered configuration items and last document locations
from the legacy `config` table to new, dedicated Dexie stores.

- Introduces a singleton `app-config` table (`AppConfigRow`) to standardize
  and structure all application settings in a single object.
- Creates a `last-locations` table for efficient storage of document read positions.
- Updates `ConfigContext` to utilize `dexie-react-hooks`' `useLiveQuery`
  for reactive and simplified state management.
- Implements a database upgrade path (from DB_VERSION 4 to 5) to migrate
  all existing user settings seamlessly.
- Simplifies config access and updates with new `getAppConfig` and `updateAppConfig`
  utility functions.
- Removes the deprecated `config` table after successful migration.
- Updates consumers like `SettingsModal` and test helpers to align with
  the new config structure.

Author: richardr1126

playwright.config.ts

@@ -11,7 +11,7 @@ export default defineConfig({
   /* Fail the build on CI if you accidentally left test.only in the source code. */
   forbidOnly: !!process.env.CI,
   retries: process.env.CI ? 2 : 0,
-  workers: process.env.CI ? '100%' : '50%',
+  // workers: '50%',
   /* Reporter to use. See https://playwright.dev/docs/test-reporters */
   reporter: 'html',
   /* Shared settings for all the projects below. See https://playwright.dev/docs/api/class-testoptions. */

src/components/SettingsModal.tsx

@@ -22,7 +22,7 @@ import {
 import { useTheme } from '@/contexts/ThemeContext';
 import { useConfig } from '@/contexts/ConfigContext';
 import { ChevronUpDownIcon, CheckIcon, SettingsIcon } from '@/components/icons/Icons';
-import { syncDocumentsToServer, loadDocumentsFromServer, setItem, getItem } from '@/utils/dexie';
+import { syncDocumentsToServer, loadDocumentsFromServer, getFirstVisit, setFirstVisit } from '@/utils/dexie';
 import { useDocuments } from '@/contexts/DocumentContext';
 import { ConfirmDialog } from '@/components/ConfirmDialog';
 import { ProgressPopup } from '@/components/ProgressPopup';
@@ -122,9 +122,9 @@ export function SettingsModal() {
   // set firstVisit on initial load
   const checkFirstVist = useCallback(async () => {
     if (!isDev) return;
-    const firstVisit = await getItem('firstVisit');
-    if (firstVisit == null) {
-      await setItem('firstVisit', 'true');
+    const firstVisit = await getFirstVisit();
+    if (!firstVisit) {
+      await setFirstVisit(true);
       setIsOpen(true);
     }
   }, [setIsOpen]);