Remove dead `drizzle-orm` import from markdown-viewer.tsx

[MODSetter]

Description

In markdown-viewer.tsx, is is imported from drizzle-orm (line 7) but never used in the file. This unnecessarily drags ORM code into a UI component's bundle chunk.

File to change

• surfsense_web/components/markdown-viewer.tsx (line 7)

Current code

import { createCodePlugin } from "@streamdown/code";
import { createMathPlugin } from "@streamdown/math";
import { Streamdown, type StreamdownProps } from "streamdown";
import "katex/dist/katex.min.css";
import { cn } from "@/lib/utils";
import Image from 'next/image';
import { is } from "drizzle-orm"; // UNUSED

What to do

Delete line 7:

- import { is } from "drizzle-orm";

Acceptance criteria

• The unused drizzle-orm import is removed
• markdown-viewer.tsx still works correctly
• next build succeeds