feat(config): add system configuration module (Phase 3)

Implement the complete erp-config crate with:
- Data dictionaries (CRUD + items management)
- Dynamic menus (tree structure with role filtering)
- System settings (hierarchical: platform > tenant > org > user)
- Numbering rules (concurrency-safe via PostgreSQL advisory_lock)
- Theme and language configuration (via settings store)
- 6 database migrations (dictionaries, menus, settings, numbering_rules)
- Frontend Settings page with 5 tabs (dictionary, menu, numbering, settings, theme)

Refactor: move RBAC functions (require_permission) from erp-auth to erp-core
to avoid cross-module dependencies.

Add 20 new seed permissions for config module operations.

apps/web/src/pages/settings/ThemeSettings.tsx

@@ -0,0 +1,104 @@
+import { useState, useEffect, useCallback } from 'react';
+import { Form, Input, Select, Button, ColorPicker, message, Typography } from 'antd';
+import client from '../../api/client';
+
+// --- Types ---
+
+interface ThemeConfig {
+  primary_color?: string;
+  logo_url?: string;
+  sidebar_style?: 'light' | 'dark';
+}
+
+// --- Component ---
+
+export default function ThemeSettings() {
+  const [form] = Form.useForm();
+  const [loading, setLoading] = useState(false);
+  const [saving, setSaving] = useState(false);
+
+  const fetchTheme = useCallback(async () => {
+    setLoading(true);
+    try {
+      const { data: resp } = await client.get('/config/themes');
+      const theme: ThemeConfig = resp.data ?? resp;
+      form.setFieldsValue({
+        primary_color: theme.primary_color || '#1677ff',
+        logo_url: theme.logo_url || '',
+        sidebar_style: theme.sidebar_style || 'light',
+      });
+    } catch {
+      // Theme may not exist yet; use defaults
+      form.setFieldsValue({
+        primary_color: '#1677ff',
+        logo_url: '',
+        sidebar_style: 'light',
+      });
+    }
+    setLoading(false);
+  }, [form]);
+
+  useEffect(() => {
+    fetchTheme();
+  }, [fetchTheme]);
+
+  const handleSave = async (values: {
+    primary_color: string;
+    logo_url: string;
+    sidebar_style: 'light' | 'dark';
+  }) => {
+    setSaving(true);
+    try {
+      await client.put('/config/themes', {
+        primary_color:
+          typeof values.primary_color === 'string'
+            ? values.primary_color
+            : (values.primary_color as { toHexString?: () => string }).toHexString?.() ?? String(values.primary_color),
+        logo_url: values.logo_url,
+        sidebar_style: values.sidebar_style,
+      });
+      message.success('主题设置已保存');
+    } catch (err: unknown) {
+      const errorMsg =
+        (err as { response?: { data?: { message?: string } } })?.response?.data
+          ?.message || '保存失败';
+      message.error(errorMsg);
+    }
+    setSaving(false);
+  };
+
+  return (
+    <div>
+      <Typography.Title level={5} style={{ marginBottom: 16 }}>
+        主题设置
+      </Typography.Title>
+
+      <Form
+        form={form}
+        onFinish={handleSave}
+        layout="vertical"
+        style={{ maxWidth: 480 }}
+      >
+        <Form.Item name="primary_color" label="主色调">
+          <ColorPicker format="hex" />
+        </Form.Item>
+        <Form.Item name="logo_url" label="Logo URL">
+          <Input placeholder="https://example.com/logo.png" />
+        </Form.Item>
+        <Form.Item name="sidebar_style" label="侧边栏风格">
+          <Select
+            options={[
+              { label: '亮色', value: 'light' },
+              { label: '暗色', value: 'dark' },
+            ]}
+          />
+        </Form.Item>
+        <Form.Item>
+          <Button type="primary" htmlType="submit" loading={saving}>
+            保存
+          </Button>
+        </Form.Item>
+      </Form>
+    </div>
+  );
+}