feat(schemas): T23 add Pydantic API key schemas

- Add ApiKeyCreate schema with OpenRouter key format validation
- Add ApiKeyUpdate schema for partial updates
- Add ApiKeyResponse schema (excludes key value for security)
- Add ApiKeyListResponse schema for pagination
- Export schemas from __init__.py
- 100% coverage on new module (23 tests)

Refs: T23

src/openrouter_monitor/schemas/__init__.py

@@ -1,4 +1,10 @@
 """Schemas package for OpenRouter Monitor."""
+from openrouter_monitor.schemas.api_key import (
+    ApiKeyCreate,
+    ApiKeyListResponse,
+    ApiKeyResponse,
+    ApiKeyUpdate,
+)
 from openrouter_monitor.schemas.auth import (
     TokenData,
     TokenResponse,
@@ -13,4 +19,8 @@ __all__ = [
     "UserResponse",
     "TokenResponse",
     "TokenData",
+    "ApiKeyCreate",
+    "ApiKeyUpdate",
+    "ApiKeyResponse",
+    "ApiKeyListResponse",
 ]

src/openrouter_monitor/schemas/api_key.py

@@ -0,0 +1,138 @@
+"""API Key Pydantic schemas.
+
+T23: Pydantic schemas for API key management.
+"""
+from datetime import datetime
+from typing import List, Optional
+
+from pydantic import BaseModel, ConfigDict, Field, field_validator
+
+
+class ApiKeyCreate(BaseModel):
+    """Schema for creating a new API key.
+    
+    Attributes:
+        name: Human-readable name for the key (1-100 chars)
+        key: OpenRouter API key (must start with 'sk-or-v1-')
+    """
+    
+    name: str = Field(
+        ...,
+        min_length=1,
+        max_length=100,
+        description="Human-readable name for the API key",
+        examples=["Production Key"]
+    )
+    key: str = Field(
+        ...,
+        description="OpenRouter API key",
+        examples=["sk-or-v1-abc123..."]
+    )
+    
+    @field_validator('key')
+    @classmethod
+    def validate_key_format(cls, v: str) -> str:
+        """Validate OpenRouter API key format.
+        
+        Args:
+            v: The API key value to validate
+            
+        Returns:
+            The API key if valid
+            
+        Raises:
+            ValueError: If key doesn't start with 'sk-or-v1-'
+        """
+        if not v or not v.strip():
+            raise ValueError("API key cannot be empty")
+        
+        if not v.startswith('sk-or-v1-'):
+            raise ValueError("API key must start with 'sk-or-v1-'")
+        
+        return v
+
+
+class ApiKeyUpdate(BaseModel):
+    """Schema for updating an existing API key.
+    
+    All fields are optional - only provided fields will be updated.
+    
+    Attributes:
+        name: New name for the key (optional, 1-100 chars)
+        is_active: Whether the key should be active (optional)
+    """
+    
+    name: Optional[str] = Field(
+        default=None,
+        min_length=1,
+        max_length=100,
+        description="New name for the API key",
+        examples=["Updated Key Name"]
+    )
+    is_active: Optional[bool] = Field(
+        default=None,
+        description="Whether the key should be active",
+        examples=[True, False]
+    )
+
+
+class ApiKeyResponse(BaseModel):
+    """Schema for API key response (returned to client).
+    
+    Note: The actual API key value is NEVER included in responses
+    for security reasons.
+    
+    Attributes:
+        id: API key ID
+        name: API key name
+        is_active: Whether the key is active
+        created_at: When the key was created
+        last_used_at: When the key was last used (None if never used)
+    """
+    
+    model_config = ConfigDict(from_attributes=True)
+    
+    id: int = Field(
+        ...,
+        description="API key ID",
+        examples=[1]
+    )
+    name: str = Field(
+        ...,
+        description="API key name",
+        examples=["Production Key"]
+    )
+    is_active: bool = Field(
+        ...,
+        description="Whether the key is active",
+        examples=[True]
+    )
+    created_at: datetime = Field(
+        ...,
+        description="When the key was created",
+        examples=["2024-01-01T12:00:00"]
+    )
+    last_used_at: Optional[datetime] = Field(
+        default=None,
+        description="When the key was last used",
+        examples=["2024-01-02T15:30:00"]
+    )
+
+
+class ApiKeyListResponse(BaseModel):
+    """Schema for paginated list of API keys.
+    
+    Attributes:
+        items: List of API key responses
+        total: Total number of keys (for pagination)
+    """
+    
+    items: List[ApiKeyResponse] = Field(
+        ...,
+        description="List of API keys"
+    )
+    total: int = Field(
+        ...,
+        description="Total number of API keys",
+        examples=[10]
+    )