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/media.py

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+"""
+Media type detection and handling utilities.
+"""
+
+from pathlib import Path
+from typing import Optional
+import mimetypes
+
+# Initialize mimetypes database
+mimetypes.init()
+
+# Media type categories
+VIDEO_TYPES = {"video/mp4", "video/webm", "video/quicktime", "video/x-msvideo", "video/avi"}
+IMAGE_TYPES = {"image/jpeg", "image/png", "image/gif", "image/webp", "image/svg+xml"}
+AUDIO_TYPES = {"audio/mpeg", "audio/wav", "audio/ogg", "audio/flac", "audio/aac", "audio/mp3"}
+
+# File extension mappings
+EXTENSION_TO_CATEGORY = {
+    # Video
+    ".mp4": "video",
+    ".webm": "video",
+    ".mov": "video",
+    ".avi": "video",
+    ".mkv": "video",
+    # Image
+    ".jpg": "image",
+    ".jpeg": "image",
+    ".png": "image",
+    ".gif": "image",
+    ".webp": "image",
+    ".svg": "image",
+    # Audio
+    ".mp3": "audio",
+    ".wav": "audio",
+    ".ogg": "audio",
+    ".flac": "audio",
+    ".aac": "audio",
+    ".m4a": "audio",
+}
+
+
+def detect_media_type(path: Path) -> str:
+    """
+    Detect the media category for a file.
+
+    Args:
+        path: Path to the file
+
+    Returns:
+        Category string: "video", "image", "audio", or "unknown"
+    """
+    if not path:
+        return "unknown"
+
+    # Try extension first
+    ext = path.suffix.lower()
+    if ext in EXTENSION_TO_CATEGORY:
+        return EXTENSION_TO_CATEGORY[ext]
+
+    # Try mimetypes
+    mime_type, _ = mimetypes.guess_type(str(path))
+    if mime_type:
+        if mime_type in VIDEO_TYPES or mime_type.startswith("video/"):
+            return "video"
+        if mime_type in IMAGE_TYPES or mime_type.startswith("image/"):
+            return "image"
+        if mime_type in AUDIO_TYPES or mime_type.startswith("audio/"):
+            return "audio"
+
+    return "unknown"
+
+
+def get_mime_type(path: Path) -> str:
+    """
+    Get the MIME type for a file.
+
+    Args:
+        path: Path to the file
+
+    Returns:
+        MIME type string or "application/octet-stream"
+    """
+    mime_type, _ = mimetypes.guess_type(str(path))
+    return mime_type or "application/octet-stream"
+
+
+def get_media_extension(media_type: str) -> str:
+    """
+    Get the typical file extension for a media type.
+
+    Args:
+        media_type: Media category or MIME type
+
+    Returns:
+        File extension with dot (e.g., ".mp4")
+    """
+    if media_type == "video":
+        return ".mp4"
+    if media_type == "image":
+        return ".png"
+    if media_type == "audio":
+        return ".mp3"
+
+    # Try as MIME type
+    ext = mimetypes.guess_extension(media_type)
+    return ext or ""
+
+
+def is_streamable(path: Path) -> bool:
+    """
+    Check if a file type is streamable (video/audio).
+
+    Args:
+        path: Path to the file
+
+    Returns:
+        True if the file can be streamed
+    """
+    media_type = detect_media_type(path)
+    return media_type in ("video", "audio")
+
+
+def needs_conversion(path: Path, target_format: str = "mp4") -> bool:
+    """
+    Check if a video file needs format conversion.
+
+    Args:
+        path: Path to the file
+        target_format: Target format (default mp4)
+
+    Returns:
+        True if conversion is needed
+    """
+    media_type = detect_media_type(path)
+    if media_type != "video":
+        return False
+
+    ext = path.suffix.lower().lstrip(".")
+    return ext != target_format
+
+
+def get_video_src(
+    content_hash: str,
+    original_path: Optional[Path] = None,
+    is_ios: bool = False,
+) -> str:
+    """
+    Get the appropriate video source URL.
+
+    For iOS devices, prefer MP4 format.
+
+    Args:
+        content_hash: Content hash for the video
+        original_path: Optional original file path
+        is_ios: Whether the client is iOS
+
+    Returns:
+        URL path for the video source
+    """
+    if is_ios:
+        return f"/cache/{content_hash}/mp4"
+
+    if original_path and original_path.suffix.lower() in (".mp4", ".webm"):
+        return f"/cache/{content_hash}/raw"
+
+    return f"/cache/{content_hash}/mp4"