Remove unused CodeMirror dependencies

@codemirror/* (8 language packages) and codemirror were declared but
imported nowhere in src — leftovers from the removed File Manager and
Database Explorer. Dropped all nine; removes 30 packages from the install
(node_modules ~44 MB -> ~39 MB). Not bundled before (unused), so the built
output is unchanged. If the future custom CSS/JS editor needs an in-browser
code editor, add back the specific packages it uses at that point.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

app/package.json

@@ -8,15 +8,6 @@
     "build": "vite build"
   },
   "dependencies": {
-    "@codemirror/lang-css": "^6.3.1",
-    "@codemirror/lang-html": "^6.4.11",
-    "@codemirror/lang-javascript": "^6.2.5",
-    "@codemirror/lang-json": "^6.0.2",
-    "@codemirror/lang-markdown": "^6.5.0",
-    "@codemirror/lang-php": "^6.0.2",
-    "@codemirror/lang-sql": "^6.10.0",
-    "@codemirror/lang-xml": "^6.1.0",
-    "codemirror": "^6.0.2",
     "vue": "^3.5.26"
   },
   "devDependencies": {