feat(frontend): Phase C 固定企业模式 - VITE_FIXED_ENTITY_ID 支持登录无下拉/隐藏切换器

- 新增 src/utils/entity.ts: isFixedEntity/getFixedEntityId/effectiveEntityId
- Login.vue: 固定企业版隐藏企业下拉显示只读徽标, 登录直接带固定 entity_id
- MainLayout.vue: 切换器加 !isFixedEntity() 守卫, 固定版顶部显示企业 tag, logo 带企业名
- ReportCenter.vue: 页内企业切换下拉加守卫, getEntityId 固定版恒取构建锁定值
- .env.example: VITE_FIXED_ENTITY_ID 示例与说明
- 验证脚本 backend/scripts/verify_phase_c_fixed_entity_e2e.py (22项, 双build E2E全过)

frontend/src/views/Login.vue

@@ -7,7 +7,8 @@
         <el-form-item>
           <el-input v-model="form.username" placeholder="用户名" size="large" @input="onUsernameChange" />
         </el-form-item>
-        <el-form-item>
+        <!-- 固定企业版（VITE_FIXED_ENTITY_ID）：隐藏企业下拉，显示只读企业徽标 -->
+        <el-form-item v-if="!isFixedEntity()">
           <el-select v-model="form.entity_id" placeholder="选择登录公司" size="large" style="width:100%" :disabled="entities.length === 0">
             <el-option v-for="e in entities" :key="e.id" :label="e.short_name || e.name" :value="e.id">
               <span>{{ e.short_name || e.name }}</span>
@@ -15,6 +16,12 @@
             </el-option>
           </el-select>
         </el-form-item>
+        <el-form-item v-else>
+          <div class="fixed-entity-badge">
+            <span class="fe-label">登录企业</span>
+            <span class="fe-name">{{ fixedEntityLabel }}</span>
+          </div>
+        </el-form-item>
         <el-form-item><el-input v-model="form.password" type="password" placeholder="密码" size="large" show-password /></el-form-item>
         <el-form-item><el-button type="primary" size="large" style="width:100%" :loading="loading" @click="handleLogin">登 录</el-button></el-form-item>
       </el-form>
@@ -23,22 +30,34 @@
 </template>
 
 <script setup lang="ts">
-import { ref, reactive, onMounted } from 'vue'
+import { ref, reactive, computed, onMounted } from 'vue'
 import { useRouter } from 'vue-router'
 import { ElMessage } from 'element-plus'
 import { authApi } from '../api/index'
+import { isFixedEntity, getFixedEntityId } from '../utils/entity'
 
 const router = useRouter()
 const loading = ref(false)
 const entities = ref<any[]>([])
 const form = reactive({ username: 'admin', password: 'admin123', entity_id: undefined as number | undefined })
 
+// ── 固定企业模式（Phase C）：构建期锁定单一企业，隐藏下拉、登录直接带固定 entity_id ──
+const fixedMode = isFixedEntity()
+const fixedEntityId = getFixedEntityId()
+
+const fixedEntityLabel = computed(() => {
+  if (fixedEntityId === undefined) return ''
+  const e = entities.value.find((x: any) => x.id === fixedEntityId)
+  if (e) return e.short_name || e.name
+  return `企业 #${fixedEntityId}`
+})
+
 async function loadEntities(username: string) {
   try {
     const r: any = await authApi.loginEntities(username)
     entities.value = r.data || []
-    // 默认选中第一个授权企业
-    if (entities.value.length > 0 && (form.entity_id === undefined || !entities.value.some((e: any) => e.id === form.entity_id))) {
+    // 切换版：默认选中第一个授权企业；固定企业版：登录时带构建锁定值，不自动改选
+    if (!fixedMode && entities.value.length > 0 && (form.entity_id === undefined || !entities.value.some((e: any) => e.id === form.entity_id))) {
       form.entity_id = entities.value[0].id
     }
   } catch (_) {
@@ -51,13 +70,14 @@ function onUsernameChange(val: string) {
 }
 
 async function handleLogin() {
-  if (form.entity_id === undefined) {
+  const entityId = fixedMode ? fixedEntityId : form.entity_id
+  if (entityId === undefined) {
     ElMessage.warning('请选择登录公司')
     return
   }
   loading.value = true
   try {
-    const res: any = await authApi.login({ ...form, entity_id: Number(form.entity_id) })
+    const res: any = await authApi.login({ ...form, entity_id: Number(entityId) })
     localStorage.setItem('cma_token', res.token)
     localStorage.setItem('cma_user', JSON.stringify(res.user))
     localStorage.setItem('cma_entity_id', String(res.entity_id ?? res.user?.entity_id ?? 1))
@@ -77,6 +97,10 @@ onMounted(() => loadEntities(form.username))
 .login-card { background: #fff; padding: 40px; border-radius: 12px; width: 380px; text-align: center; }
 .login-card h1 { margin: 0 0 4px; font-size: 24px; }
 .subtitle { color: #999; margin-bottom: 24px; }
+/* 固定企业版登录徽标 */
+.fixed-entity-badge { display: flex; align-items: center; justify-content: center; gap: 10px; width: 100%; height: 40px; border: 1px dashed #c0c4cc; border-radius: 6px; background: #f8f9fc; padding: 0 12px; }
+.fe-label { color: #909399; font-size: 13px; }
+.fe-name { color: #303133; font-size: 14px; font-weight: 600; }
 @media screen and (max-width: 768px) {
   .login-page { padding: 20px; }
   .login-card { width: 100%; max-width: 380px; padding: 30px 24px; }