feat: add messaging system database models and core services

- Add Conversation, ConversationParticipant, Message, MessageAttachment models
- Add ConversationType enum (admin_vendor, vendor_customer, admin_customer)
- Add ParticipantType enum (admin, vendor, customer)
- Add Alembic migration for messaging tables
- Add MessagingService for conversation/message operations
- Add MessageAttachmentService for file upload handling
- Add message-related exceptions (ConversationNotFoundException, etc.)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/schema/message.py

@@ -0,0 +1,308 @@
+# models/schema/message.py
+"""
+Pydantic schemas for the messaging system.
+
+Supports three communication channels:
+- Admin <-> Vendor
+- Vendor <-> Customer
+- Admin <-> Customer
+"""
+
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict, Field
+
+from models.database.message import ConversationType, ParticipantType
+
+
+# ============================================================================
+# Attachment Schemas
+# ============================================================================
+
+
+class AttachmentResponse(BaseModel):
+    """Schema for message attachment in responses."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    filename: str
+    original_filename: str
+    file_size: int
+    mime_type: str
+    is_image: bool
+    image_width: int | None = None
+    image_height: int | None = None
+    download_url: str | None = None
+    thumbnail_url: str | None = None
+
+    @property
+    def file_size_display(self) -> str:
+        """Human-readable file size."""
+        if self.file_size < 1024:
+            return f"{self.file_size} B"
+        elif self.file_size < 1024 * 1024:
+            return f"{self.file_size / 1024:.1f} KB"
+        else:
+            return f"{self.file_size / 1024 / 1024:.1f} MB"
+
+
+# ============================================================================
+# Message Schemas
+# ============================================================================
+
+
+class MessageCreate(BaseModel):
+    """Schema for sending a new message."""
+
+    content: str = Field(..., min_length=1, max_length=10000)
+
+
+class MessageResponse(BaseModel):
+    """Schema for a single message in responses."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    conversation_id: int
+    sender_type: ParticipantType
+    sender_id: int
+    content: str
+    is_system_message: bool
+    is_deleted: bool
+    created_at: datetime
+
+    # Enriched sender info (populated by API)
+    sender_name: str | None = None
+    sender_email: str | None = None
+
+    # Attachments
+    attachments: list[AttachmentResponse] = []
+
+
+# ============================================================================
+# Participant Schemas
+# ============================================================================
+
+
+class ParticipantInfo(BaseModel):
+    """Schema for participant information."""
+
+    id: int
+    type: ParticipantType
+    name: str
+    email: str | None = None
+    avatar_url: str | None = None
+
+
+class ParticipantResponse(BaseModel):
+    """Schema for conversation participant in responses."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    participant_type: ParticipantType
+    participant_id: int
+    unread_count: int
+    last_read_at: datetime | None
+    email_notifications: bool
+    muted: bool
+
+    # Enriched info (populated by API)
+    participant_info: ParticipantInfo | None = None
+
+
+# ============================================================================
+# Conversation Schemas
+# ============================================================================
+
+
+class ConversationCreate(BaseModel):
+    """Schema for creating a new conversation."""
+
+    conversation_type: ConversationType
+    subject: str = Field(..., min_length=1, max_length=500)
+    recipient_type: ParticipantType
+    recipient_id: int
+    vendor_id: int | None = None
+    initial_message: str | None = Field(None, min_length=1, max_length=10000)
+
+
+class ConversationSummary(BaseModel):
+    """Schema for conversation in list views."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    conversation_type: ConversationType
+    subject: str
+    vendor_id: int | None = None
+    is_closed: bool
+    closed_at: datetime | None
+    last_message_at: datetime | None
+    message_count: int
+    created_at: datetime
+
+    # Unread count for current user (from participant)
+    unread_count: int = 0
+
+    # Other participant info (enriched by API)
+    other_participant: ParticipantInfo | None = None
+
+    # Last message preview
+    last_message_preview: str | None = None
+
+
+class ConversationDetailResponse(BaseModel):
+    """Schema for full conversation detail with messages."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    conversation_type: ConversationType
+    subject: str
+    vendor_id: int | None = None
+    is_closed: bool
+    closed_at: datetime | None
+    closed_by_type: ParticipantType | None = None
+    closed_by_id: int | None = None
+    last_message_at: datetime | None
+    message_count: int
+    created_at: datetime
+    updated_at: datetime
+
+    # Participants with enriched info
+    participants: list[ParticipantResponse] = []
+
+    # Messages ordered by created_at
+    messages: list[MessageResponse] = []
+
+    # Current user's unread count
+    unread_count: int = 0
+
+    # Vendor info if applicable
+    vendor_name: str | None = None
+
+
+class ConversationListResponse(BaseModel):
+    """Schema for paginated conversation list."""
+
+    conversations: list[ConversationSummary]
+    total: int
+    total_unread: int
+    skip: int
+    limit: int
+
+
+# ============================================================================
+# Unread Count Schemas
+# ============================================================================
+
+
+class UnreadCountResponse(BaseModel):
+    """Schema for unread message count (for header badge)."""
+
+    total_unread: int
+
+
+# ============================================================================
+# Notification Preferences Schemas
+# ============================================================================
+
+
+class NotificationPreferencesUpdate(BaseModel):
+    """Schema for updating notification preferences."""
+
+    email_notifications: bool | None = None
+    muted: bool | None = None
+
+
+# ============================================================================
+# Conversation Action Schemas
+# ============================================================================
+
+
+class CloseConversationResponse(BaseModel):
+    """Response after closing a conversation."""
+
+    success: bool
+    message: str
+    conversation_id: int
+
+
+class ReopenConversationResponse(BaseModel):
+    """Response after reopening a conversation."""
+
+    success: bool
+    message: str
+    conversation_id: int
+
+
+class MarkReadResponse(BaseModel):
+    """Response after marking conversation as read."""
+
+    success: bool
+    conversation_id: int
+    unread_count: int
+
+
+# ============================================================================
+# Recipient Selection Schemas (for compose modal)
+# ============================================================================
+
+
+class RecipientOption(BaseModel):
+    """Schema for a selectable recipient in compose modal."""
+
+    id: int
+    type: ParticipantType
+    name: str
+    email: str | None = None
+    vendor_id: int | None = None  # For vendor users
+    vendor_name: str | None = None
+
+
+class RecipientListResponse(BaseModel):
+    """Schema for list of available recipients."""
+
+    recipients: list[RecipientOption]
+    total: int
+
+
+# ============================================================================
+# Admin-specific Schemas
+# ============================================================================
+
+
+class AdminConversationSummary(ConversationSummary):
+    """Extended conversation summary with vendor info for admin views."""
+
+    vendor_name: str | None = None
+    vendor_code: str | None = None
+
+
+class AdminConversationListResponse(BaseModel):
+    """Schema for admin conversation list with vendor info."""
+
+    conversations: list[AdminConversationSummary]
+    total: int
+    total_unread: int
+    skip: int
+    limit: int
+
+
+class AdminMessageStats(BaseModel):
+    """Messaging statistics for admin dashboard."""
+
+    total_conversations: int = 0
+    open_conversations: int = 0
+    closed_conversations: int = 0
+    total_messages: int = 0
+
+    # By type
+    admin_vendor_conversations: int = 0
+    vendor_customer_conversations: int = 0
+    admin_customer_conversations: int = 0
+
+    # Unread
+    unread_admin: int = 0