feat(converter): add shareable conversion links via query parameters

app/page.tsx

@@ -1,10 +1,11 @@
 "use client";
 
-import { useCallback, useState } from "react";
+import { useCallback, useEffect, useState } from "react";
 
 import { ConverterCard } from "@/components/converter/converter-card";
 import { Hero } from "@/components/sections/hero";
 import { InsightsSection } from "@/components/sections/insights-section";
+import { parseConversionShareParams } from "@/lib/share-link";
 
 const DEFAULT_FROM = "USD";
 const DEFAULT_TO = "BTC";
@@ -12,6 +13,29 @@ const DEFAULT_TO = "BTC";
 export default function HomePage() {
   const [selectedFromCode, setSelectedFromCode] = useState(DEFAULT_FROM);
   const [selectedToCode, setSelectedToCode] = useState(DEFAULT_TO);
+  const [forcedAmount, setForcedAmount] = useState<string | undefined>(
+    undefined,
+  );
+
+  useEffect(() => {
+    if (typeof window === "undefined") {
+      return;
+    }
+
+    const parsed = parseConversionShareParams(
+      new URLSearchParams(window.location.search),
+    );
+
+    if (parsed.fromCode) {
+      setSelectedFromCode(parsed.fromCode);
+    }
+
+    if (parsed.toCode) {
+      setSelectedToCode(parsed.toCode);
+    }
+
+    setForcedAmount(parsed.amount);
+  }, []);
 
   const handleSelectPopularPair = useCallback(
     (fromCode: string, toCode: string) => {
@@ -34,6 +58,7 @@ export default function HomePage() {
           <ConverterCard
             forcedFromCode={selectedFromCode}
             forcedToCode={selectedToCode}
+            forcedAmount={forcedAmount}
             onPairChange={handlePairChange}
           />
           <InsightsSection