Use mime_guess for file extension MIME type detection

Replace the hand-maintained extension-to-MIME mapping with the
mime_guess crate, which was already in the dependency tree.
This covers hundreds of file extensions out of the box.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/utils/mime.rs

@@ -17,30 +17,7 @@ pub fn get_file_extension(mime_type: &mime::Mime) -> String {
 }
 
 pub fn get_mime_type_from_file_name(file_name: &str) -> mime::Mime {
-    let extension = file_name.rsplit('.').next().unwrap_or("");
-
-    match extension.to_lowercase().as_str() {
-        "jpg" | "jpeg" => mime::IMAGE_JPEG,
-        "png" => mime::IMAGE_PNG,
-        "gif" => mime::IMAGE_GIF,
-        "webp" => "image/webp".parse().unwrap(),
-        "svg" => mime::IMAGE_SVG,
-        "tiff" | "tif" => "image/tiff".parse().unwrap(),
-        "bmp" => "image/bmp".parse().unwrap(),
-        "heic" | "heif" => "image/heic".parse().unwrap(),
-        "avif" => "image/avif".parse().unwrap(),
-        "pdf" => "application/pdf".parse().unwrap(),
-        "txt" | "log" => mime::TEXT_PLAIN,
-        "csv" => mime::TEXT_CSV,
-        "json" => mime::APPLICATION_JSON,
-        "xml" => "application/xml".parse().unwrap(),
-        "html" | "htm" => mime::TEXT_HTML,
-        "md" | "markdown" => "text/markdown".parse().unwrap(),
-        "yaml" | "yml" => "application/yaml".parse().unwrap(),
-        "toml" => "application/toml".parse().unwrap(),
-        "rs" | "py" | "js" | "ts" | "go" | "c" | "cpp" | "h" | "java" | "rb" | "sh" | "css" => {
-            mime::TEXT_PLAIN
-        }
-        _ => mime::APPLICATION_OCTET_STREAM,
-    }
+    mime_guess::from_path(file_name)
+        .first()
+        .unwrap_or(mime::APPLICATION_OCTET_STREAM)
 }