feat(ui): truncate long file names and auto-close context menu

- Add `.file-name` class with ellipsis truncation for long file names to prevent layout overflow.
- Apply truncation to metadata and file items in download and preview pages.
- Add `title` attributes to truncated names to show the full text on hover.
- Automatically close the file context menu when the mouse moves more than 80px away from it.

backend/static/js/app.js

@@ -19,6 +19,7 @@
   const fileContextMenu = document.querySelector("[data-file-context-menu]");
   let ctrlCopyMode = false;
   let contextFile = null;
+  const contextMenuCloseDistance = 80;
 
   if (fileBrowser) {
     viewButtons.forEach((button) => {
@@ -79,6 +80,13 @@
       }
     });
 
+    document.addEventListener("mousemove", (event) => {
+      if (fileContextMenu.hidden || isPointerNearContextMenu(event.clientX, event.clientY)) {
+        return;
+      }
+      hideContextMenu();
+    });
+
     window.addEventListener("resize", hideContextMenu);
     window.addEventListener("scroll", hideContextMenu, true);
   }
@@ -295,7 +303,9 @@
 
     const body = document.createElement("span");
     const name = document.createElement("strong");
+    name.className = "file-name";
     name.textContent = file.name;
+    name.title = file.name;
     const meta = document.createElement("code");
     meta.textContent = file.meta;
     body.append(name, meta);
@@ -428,6 +438,14 @@
     contextFile = null;
   }
 
+  function isPointerNearContextMenu(x, y) {
+    const rect = fileContextMenu.getBoundingClientRect();
+    return x >= rect.left - contextMenuCloseDistance &&
+      x <= rect.right + contextMenuCloseDistance &&
+      y >= rect.top - contextMenuCloseDistance &&
+      y <= rect.bottom + contextMenuCloseDistance;
+  }
+
   function openInNewTab(url) {
     window.open(url, "_blank", "noopener,noreferrer");
   }