feat(models): 组织、用户、角色、客户、会话与消息模型

按组织边界定义数据关系，补齐仓储层与通用工具，迁移脚本可重复执行。

backend/app/models/schemas/help_center.py

@@ -0,0 +1,151 @@
+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+import re
+from datetime import datetime
+from typing import List, Optional
+from uuid import UUID
+
+from pydantic import BaseModel, ConfigDict, Field, field_validator
+
+from app.models.help_center import DomainStatus, SSLStatus
+from app.utils.urls import normalize_url
+
+MAX_HEADER_LINKS = 6
+_HEX_COLOR_RE = re.compile(r"^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6}|[0-9a-fA-F]{8})$")
+# RFC 1035-ish hostname: labels of letters/digits/hyphens, at least one dot.
+# The TLD alternation admits punycode labels (xn--...) that IDNA encoding of
+# internationalized domains produces.
+_HOSTNAME_RE = re.compile(
+    r"^(?=.{4,253}$)([a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\.)+(?:[a-z]{2,}|xn--[a-z0-9-]{2,})$"
+)
+
+
+class HeaderLink(BaseModel):
+    label: str = Field(min_length=1, max_length=40)
+    url: str = Field(min_length=1, max_length=2048)
+
+    @field_validator("url")
+    @classmethod
+    def _url(cls, v: str) -> str:
+        # Raises on blank/whitespace input rather than returning None into a
+        # non-optional str field.
+        return normalize_url(v)
+
+
+class HelpCenterSettingsUpdate(BaseModel):
+    enabled: Optional[bool] = None
+    title: Optional[str] = Field(default=None, max_length=120)
+    description: Optional[str] = Field(default=None, max_length=300)
+    brand_color: Optional[str] = None
+    header_links: Optional[List[HeaderLink]] = Field(default=None, max_length=MAX_HEADER_LINKS)
+    cta_text: Optional[str] = Field(default=None, max_length=40)
+    cta_url: Optional[str] = Field(default=None, max_length=2048)
+    cta_enabled: Optional[bool] = None
+    auto_generate: Optional[bool] = None
+    agent_id: Optional[UUID] = None
+    ai_search_enabled: Optional[bool] = None
+    chat_widget_enabled: Optional[bool] = None
+
+    @field_validator("brand_color")
+    @classmethod
+    def _hex_color(cls, v: Optional[str]) -> Optional[str]:
+        if v is None:
+            return None
+        v = v.strip()
+        if not _HEX_COLOR_RE.match(v):
+            raise ValueError("brand_color must be a hex color like #4338CA")
+        return v
+
+    @field_validator("cta_url")
+    @classmethod
+    def _cta_url(cls, v: Optional[str]) -> Optional[str]:
+        # Blank clears the CTA link; anything else is normalized.
+        if v is None or not v.strip():
+            return None
+        return normalize_url(v)
+
+
+class HelpCenterAgentOption(BaseModel):
+    """Org agents offered in the AI-search agent selector."""
+    id: UUID
+    name: str
+    has_widget: bool
+
+
+class DnsRecord(BaseModel):
+    """One row of the DNS-records table in the admin UI."""
+    type: str  # CNAME | TXT
+    host: str
+    value: str
+    verified: bool
+
+
+class DomainStatusResponse(BaseModel):
+    custom_domain: Optional[str] = None
+    domain_status: DomainStatus
+    ssl_status: SSLStatus
+    records: List[DnsRecord] = []
+    domain_verified_at: Optional[datetime] = None
+
+
+class HelpCenterSettingsResponse(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    enabled: bool
+    slug: Optional[str] = None
+    title: Optional[str] = None
+    description: Optional[str] = None
+    logo_url: Optional[str] = None
+    favicon_url: Optional[str] = None
+    brand_color: str
+    header_links: List[HeaderLink] = []
+    cta_text: Optional[str] = None
+    cta_url: Optional[str] = None
+    cta_enabled: bool
+    auto_generate: bool
+    agent_id: Optional[UUID] = None
+    ai_search_enabled: bool
+    chat_widget_enabled: bool
+
+    # Enriched by the API layer (not ORM columns):
+    live_url: Optional[str] = None
+    published_count: int = 0
+    plan_allowed: bool = True
+    agents: List[HelpCenterAgentOption] = []
+    domain: Optional[DomainStatusResponse] = None
+
+    @field_validator("header_links", mode="before")
+    @classmethod
+    def _coerce_null_json(cls, v):
+        return v or []
+
+
+class DomainRequest(BaseModel):
+    domain: str = Field(min_length=4, max_length=255)
+
+    @field_validator("domain")
+    @classmethod
+    def _hostname(cls, v: str) -> str:
+        v = v.strip().lower().rstrip(".")
+        v = re.sub(r"^https?://", "", v).split("/")[0]
+        try:
+            v = v.encode("idna").decode("ascii")
+        except UnicodeError as exc:
+            raise ValueError("domain is not a valid hostname") from exc
+        if not _HOSTNAME_RE.match(v):
+            raise ValueError("domain is not a valid hostname")
+        return v