feat: add create and delete file/folder functionality to editor

- Add Tauri backend commands: create_file, create_directory, delete_file, delete_directory
- Add editor store functions for create/delete with auto-refresh
- Add FileContextMenu component with right-click support
- Add InputDialog component for file/folder name input
- Add ConfirmDialog component for delete confirmation
- Add Ctrl+N keyboard shortcut for new file
- Update keyboard shortcuts modal with new shortcuts
- Auto-close tabs when their files are deleted
- Auto-refresh file tree after create/delete operations

src/lib/components/editor/FileContextMenu.svelte

@@ -0,0 +1,110 @@
+<script lang="ts">
+  import type { FileEntry } from "$lib/types/editor";
+
+  interface Props {
+    x: number;
+    y: number;
+    targetEntry: FileEntry | null;
+    currentDirectory: string;
+    onNewFile: (parentPath: string) => void;
+    onNewFolder: (parentPath: string) => void;
+    onDelete: (entry: FileEntry) => void;
+    onClose: () => void;
+  }
+
+  let { x, y, targetEntry, currentDirectory, onNewFile, onNewFolder, onDelete, onClose }: Props =
+    $props();
+
+  function handleNewFile() {
+    const parentPath = targetEntry?.isDirectory ? targetEntry.path : currentDirectory;
+    onNewFile(parentPath);
+    onClose();
+  }
+
+  function handleNewFolder() {
+    const parentPath = targetEntry?.isDirectory ? targetEntry.path : currentDirectory;
+    onNewFolder(parentPath);
+    onClose();
+  }
+
+  function handleDelete() {
+    if (targetEntry) {
+      onDelete(targetEntry);
+      onClose();
+    }
+  }
+
+  function handleKeydown(event: KeyboardEvent) {
+    if (event.key === "Escape") {
+      onClose();
+    }
+  }
+</script>
+
+<svelte:window onkeydown={handleKeydown} />
+
+<!-- svelte-ignore a11y_no_static_element_interactions -->
+<div
+  class="fixed inset-0 z-50"
+  onclick={onClose}
+  oncontextmenu={(e) => {
+    e.preventDefault();
+    onClose();
+  }}
+>
+  <!-- svelte-ignore a11y_no_static_element_interactions -->
+  <div
+    class="absolute z-50 min-w-[160px] rounded-md border border-gray-700 bg-gray-800 py-1 shadow-lg"
+    style="left: {x}px; top: {y}px;"
+    onclick={(e) => e.stopPropagation()}
+  >
+    <button
+      class="flex w-full items-center gap-2 px-3 py-1.5 text-left text-sm text-gray-200 hover:bg-gray-700"
+      onclick={handleNewFile}
+    >
+      <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+        <path
+          stroke-linecap="round"
+          stroke-linejoin="round"
+          stroke-width="2"
+          d="M9 13h6m-3-3v6m5 5H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z"
+        />
+      </svg>
+      New File
+    </button>
+
+    <button
+      class="flex w-full items-center gap-2 px-3 py-1.5 text-left text-sm text-gray-200 hover:bg-gray-700"
+      onclick={handleNewFolder}
+    >
+      <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+        <path
+          stroke-linecap="round"
+          stroke-linejoin="round"
+          stroke-width="2"
+          d="M9 13h6m-3-3v6m-9 1V7a2 2 0 012-2h6l2 2h6a2 2 0 012 2v8a2 2 0 01-2 2H5a2 2 0 01-2-2z"
+        />
+      </svg>
+      New Folder
+    </button>
+
+    {#if targetEntry}
+      <div class="my-1 border-t border-gray-700"></div>
+
+      <button
+        class="flex w-full items-center gap-2 px-3 py-1.5 text-left text-sm text-red-400 hover:bg-gray-700"
+        onclick={handleDelete}
+      >
+        <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+          <path
+            stroke-linecap="round"
+            stroke-linejoin="round"
+            stroke-width="2"
+            d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
+          />
+        </svg>
+        Delete {targetEntry.isDirectory ? "Folder" : "File"}
+      </button>
+    {/if}
+  </div>
+</div>