refactor: 移除前端 Mock API，新增共享组件，优化认证流程

- 删除 mock_api_client、mock_calendar_service、mock_history_service
- 新增 fixed_length_code_input、link_button、message_composer 共享组件
- 优化登录/注册/密码重置页面使用新组件
- 简化 injection.dart 移除 mock 分支
- 更新 env.dart 配置（BACKEND_URL 替换 API_URL）
- 后端 agentscope 工具和测试更新
- 重构 AGENTS.md 文档结构
- 新增 deploy/ 目录和 protocol 文档

backend/alembic/versions/20260227_0006_invite_codes_and_profile_referral.py

@@ -20,7 +20,7 @@ def upgrade() -> None:
         """
         CREATE TABLE invite_codes (
             id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
-            code VARCHAR(8) NOT NULL UNIQUE CHECK (code ~ '^[ABCDEFGHJKMNPQRSTUVWXYZ23456789]{8}$'),
+            code VARCHAR(4) NOT NULL UNIQUE CHECK (code ~ '^[ABCDEFGHJKMNPQRSTUVWXYZ23456789]{4}$'),
             owner_id UUID REFERENCES profiles(id) ON DELETE SET NULL,
             status VARCHAR(20) NOT NULL DEFAULT 'active' CHECK (status IN ('active', 'disabled', 'expired')),
             used_count INTEGER NOT NULL DEFAULT 0 CHECK (used_count >= 0),
@@ -63,7 +63,7 @@ def upgrade() -> None:
             result TEXT := '';
             i INT;
         BEGIN
-            FOR i IN 1..8 LOOP
+            FOR i IN 1..4 LOOP
                 result := result || substr(chars, floor(random() * length(chars) + 1)::int, 1);
             END LOOP;
             RETURN result;
@@ -126,9 +126,9 @@ def upgrade() -> None:
             END LOOP;
 
             invite_code_value := NEW.raw_user_meta_data ->> 'invite_code';
-            IF invite_code_value IS NOT NULL AND length(invite_code_value) = 8 THEN
+            IF invite_code_value IS NOT NULL AND length(invite_code_value) = 4 THEN
                 invite_code_value := upper(invite_code_value);
-                IF invite_code_value ~ '^[ABCDEFGHJKMNPQRSTUVWXYZ23456789]{8}$' THEN
+                IF invite_code_value ~ '^[ABCDEFGHJKMNPQRSTUVWXYZ23456789]{4}$' THEN
                     UPDATE public.invite_codes
                     SET used_count = used_count + 1
                     WHERE code = invite_code_value