fix(web): extract single tryGetHostname helper (DRY, unified fallback)

Fixes #1368

Previously,  was duplicated in 4 places with 3 subtly different fallback behaviors:
1. inline-citation.tsx: returned  on error
2. markdown-text.tsx: returned  on error
3. assistant-message.tsx: returned  on error
4. citation.tsx: returned  on error

Created canonical  in  that:
- Returns
- Strips  prefix from hostname
- Returns  on invalid URL (safest contract)

Updated all 4 call sites:
- inline-citation.tsx:  (preserves original fallback)
- markdown-text.tsx:  (preserves original fallback)
- assistant-message.tsx:  (drop-in, both return )
- citation.tsx:  (drop-in, both return )

Co-authored-by: guangyang1206 <guangyang1206@users.noreply.github.com>

surfsense_web/components/tool-ui/citation/citation.tsx

@@ -6,19 +6,11 @@ import * as React from "react";
 import { openSafeNavigationHref, sanitizeHref } from "../shared/media";
 import { cn, Popover, PopoverContent, PopoverTrigger } from "./_adapter";
 import type { CitationVariant, SerializableCitation } from "./schema";
+import { tryGetHostname } from "@/lib/url";
 import { TYPE_ICONS } from "./type-icons";
 
 const FALLBACK_LOCALE = "en-US";
 
-function extractDomain(url: string): string | undefined {
-	try {
-		const urlObj = new URL(url);
-		return urlObj.hostname.replace(/^www\./, "");
-	} catch {
-		return undefined;
-	}
-}
-
 function formatDate(isoString: string, locale: string): string {
 	try {
 		const date = new Date(isoString);
@@ -78,7 +70,7 @@ export function Citation(props: CitationProps) {
 
 	const locale = providedLocale ?? FALLBACK_LOCALE;
 	const sanitizedHref = sanitizeHref(rawHref);
-	const domain = providedDomain ?? extractDomain(rawHref);
+	const domain = providedDomain ?? tryGetHostname(rawHref);
 
 	const citationData: SerializableCitation = {
 		...serializable,