Initial artdag-common shared library

Shared components for L1 and L2 servers:
- Jinja2 template system with base template and components
- Middleware for auth and content negotiation
- Pydantic models for requests/responses
- Utility functions for pagination, media, formatting
- Constants for Tailwind/HTMX/Cytoscape CDNs

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

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

artdag_common/models/responses.py

@@ -0,0 +1,96 @@
+"""
+Response models shared across L1 and L2 servers.
+"""
+
+from typing import Optional, List, Dict, Any, Generic, TypeVar
+from pydantic import BaseModel, Field
+
+T = TypeVar("T")
+
+
+class PaginatedResponse(BaseModel, Generic[T]):
+    """Generic paginated response."""
+    data: List[Any] = Field(default_factory=list)
+    pagination: Dict[str, Any] = Field(default_factory=dict)
+
+    @classmethod
+    def create(
+        cls,
+        items: List[Any],
+        page: int,
+        limit: int,
+        total: int,
+    ) -> "PaginatedResponse":
+        """Create a paginated response."""
+        return cls(
+            data=items,
+            pagination={
+                "page": page,
+                "limit": limit,
+                "total": total,
+                "has_more": page * limit < total,
+                "total_pages": (total + limit - 1) // limit,
+            }
+        )
+
+
+class ErrorResponse(BaseModel):
+    """Standard error response."""
+    error: str = Field(..., description="Error message")
+    detail: Optional[str] = Field(default=None, description="Detailed error info")
+    code: Optional[str] = Field(default=None, description="Error code")
+
+
+class SuccessResponse(BaseModel):
+    """Standard success response."""
+    success: bool = Field(default=True)
+    message: Optional[str] = Field(default=None)
+    data: Optional[Dict[str, Any]] = Field(default=None)
+
+
+class RunStatus(BaseModel):
+    """Run execution status."""
+    run_id: str
+    status: str = Field(..., description="pending, running, completed, failed")
+    recipe: Optional[str] = None
+    plan_id: Optional[str] = None
+    output_hash: Optional[str] = None
+    output_ipfs_cid: Optional[str] = None
+    total_steps: int = 0
+    cached_steps: int = 0
+    completed_steps: int = 0
+    error: Optional[str] = None
+
+
+class CacheItemResponse(BaseModel):
+    """Cached content item response."""
+    content_hash: str
+    media_type: Optional[str] = None
+    size: Optional[int] = None
+    name: Optional[str] = None
+    description: Optional[str] = None
+    tags: List[str] = Field(default_factory=list)
+    ipfs_cid: Optional[str] = None
+    created_at: Optional[str] = None
+
+
+class RecipeResponse(BaseModel):
+    """Recipe response."""
+    recipe_id: str
+    name: str
+    description: Optional[str] = None
+    inputs: List[Dict[str, Any]] = Field(default_factory=list)
+    outputs: List[str] = Field(default_factory=list)
+    node_count: int = 0
+    created_at: Optional[str] = None
+
+
+class StorageProviderResponse(BaseModel):
+    """Storage provider configuration response."""
+    storage_id: str
+    provider_type: str
+    name: str
+    is_default: bool = False
+    is_connected: bool = False
+    usage_bytes: Optional[int] = None
+    pin_count: int = 0