feat(webui): Enhance dashboard, global styles, and settings module

## Dashboard Enhancements
- Add Request Volume trend chart with Chart.js line graph
  - Support Family/Model display modes for aggregation levels
  - Show Total/Today/1H usage statistics
  - Hierarchical filter dropdown with Smart select (Top 5 by 24h usage)
  - Persist chart preferences to localStorage
- Improve account health detection logic
  - Core models (sonnet/opus/pro/flash) require >5% quota to be healthy
  - Dynamic quota ring chart supporting any model family
- Unify table styles with standard-table class

## Global Style Refactoring
- Add CSS variable system for theming
  - Space color scale (950/900/850/800/border)
  - Neon accent colors (purple/green/cyan/yellow/red)
  - Text hierarchy (main/dim/muted/bright)
  - Chart palette (16 colors)
- Add unified component classes
  - .view-container for consistent page layouts
  - .section-header/.section-title/.section-desc
  - .standard-table for table styling
- Update scrollbar, nav-item, progress-bar to use theme variables

## Settings Module Extensions
- Add model mapping column in Models tab
- Enhance model selectors with family color indicators
- Support horizontal scroll for tabs on narrow screens
- Add defaultCooldownMs and maxWaitBeforeErrorMs config options

## New Module
- Add src/modules/usage-stats.js for request tracking
  - Track /v1/messages and /v1/chat/completions endpoints
  - Hierarchical storage: { hour: { family: { model: count } } }
  - Auto-save every minute, 30-day retention
  - GET /api/stats/history endpoint for dashboard chart

## Backend Changes
- Add direct account manipulation helpers (bypass AccountManager)
- Add POST /api/config/password endpoint for WebUI password change
- Auto-reload AccountManager after account operations
- Use CSS variables in OAuth callback pages

## Other
- Update .gitignore for runtime data directory
- Add i18n keys for new UI elements (EN/zh_CN)

Co-Authored-By: Claude <noreply@anthropic.com>

public/js/utils.js

@@ -13,7 +13,8 @@ window.utils = {
         let response = await fetch(url, options);
 
         if (response.status === 401) {
-            const password = prompt('Enter Web UI Password:');
+            const store = Alpine.store('global');
+            const password = prompt(store ? store.t('enterPassword') : 'Enter Web UI Password:');
             if (password) {
                 // Return new password so caller can update state
                 // This implies we need a way to propagate the new password back
@@ -31,11 +32,16 @@ window.utils = {
     },
 
     formatTimeUntil(isoTime) {
+        const store = Alpine.store('global');
         const diff = new Date(isoTime) - new Date();
-        if (diff <= 0) return 'READY';
+        if (diff <= 0) return store ? store.t('ready') : 'READY';
         const mins = Math.floor(diff / 60000);
         const hrs = Math.floor(mins / 60);
         if (hrs > 0) return `${hrs}H ${mins % 60}M`;
         return `${mins}M`;
+    },
+
+    getThemeColor(name) {
+        return getComputedStyle(document.documentElement).getPropertyValue(name).trim();
     }
 };