fix: restore KaTeX assets and deployment checks

backend/static/css/app.css

@@ -161,7 +161,9 @@ button { color: inherit; }
 .editor-pane label, .preview-pane > span { display: block; color: #9eaaa2; font-size: 10px; letter-spacing: .16em; text-transform: uppercase; }
 .editor-pane textarea { width: 100%; height: 330px; margin-top: 22px; resize: none; border: 0; outline: 0; background: transparent; color: #dcefa1; font: 16px/1.8 "SFMono-Regular", Consolas, monospace; }
 .preview-pane { display: flex; flex-direction: column; }
-#latex-preview { margin: auto; max-width: 100%; overflow-wrap: anywhere; font: 28px/1.6 Georgia, serif; }
+#latex-preview { margin: auto; max-width: 100%; overflow-x: auto; overflow-y: hidden; padding: 18px 4px; font-size: 28px; line-height: 1.6; }
+#latex-preview .katex-display { margin: 0; overflow-x: auto; overflow-y: hidden; }
+#latex-preview.latex-preview-error { color: #b84136; font: 14px/1.7 system-ui, sans-serif; white-space: normal; }
 .preview-pane button { align-self: flex-end; }
 .profile-panel { padding: 35px; }
 .metric-grid { display: grid; grid-template-columns: repeat(5, 1fr); gap: 10px; }