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/utils/pagination.py

@@ -0,0 +1,85 @@
+"""
+Pagination utilities.
+"""
+
+from typing import List, Any, Tuple, Optional
+
+from fastapi import Request
+
+from ..constants import DEFAULT_PAGE_SIZE, MAX_PAGE_SIZE
+
+
+def get_pagination_params(request: Request) -> Tuple[int, int]:
+    """
+    Extract pagination parameters from request query string.
+
+    Args:
+        request: FastAPI request
+
+    Returns:
+        Tuple of (page, limit)
+    """
+    try:
+        page = int(request.query_params.get("page", 1))
+        page = max(1, page)
+    except ValueError:
+        page = 1
+
+    try:
+        limit = int(request.query_params.get("limit", DEFAULT_PAGE_SIZE))
+        limit = max(1, min(limit, MAX_PAGE_SIZE))
+    except ValueError:
+        limit = DEFAULT_PAGE_SIZE
+
+    return page, limit
+
+
+def paginate(
+    items: List[Any],
+    page: int = 1,
+    limit: int = DEFAULT_PAGE_SIZE,
+) -> Tuple[List[Any], dict]:
+    """
+    Paginate a list of items.
+
+    Args:
+        items: Full list of items
+        page: Page number (1-indexed)
+        limit: Items per page
+
+    Returns:
+        Tuple of (paginated items, pagination info dict)
+    """
+    total = len(items)
+    start = (page - 1) * limit
+    end = start + limit
+
+    paginated = items[start:end]
+
+    return paginated, {
+        "page": page,
+        "limit": limit,
+        "total": total,
+        "has_more": end < total,
+        "total_pages": (total + limit - 1) // limit if total > 0 else 1,
+    }
+
+
+def calculate_offset(page: int, limit: int) -> int:
+    """Calculate database offset from page and limit."""
+    return (page - 1) * limit
+
+
+def build_pagination_info(
+    page: int,
+    limit: int,
+    total: int,
+) -> dict:
+    """Build pagination info dictionary."""
+    return {
+        "page": page,
+        "limit": limit,
+        "total": total,
+        "has_more": page * limit < total,
+        "total_pages": (total + limit - 1) // limit if total > 0 else 1,
+    }