feat: add app logo as favicon for main and downloads pages

Author: begin0808

docs/download_page.html

@@ -5,6 +5,8 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Studio0808 :: 檔案下載與版本更新</title>
+    <link rel="icon" href="app.png" type="image/png">
+    <link rel="shortcut icon" href="app.png" type="image/png">
     <style>
         :root {
             --primary: #29B6F6;

docs/download_page_en.html

@@ -5,6 +5,8 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Studio0808 :: Downloads & Version Updates</title>
+    <link rel="icon" href="app.png" type="image/png">
+    <link rel="shortcut icon" href="app.png" type="image/png">
     <style>
         :root {
             --primary: #29B6F6;

docs/index.html

@@ -5,6 +5,8 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Studio0808 AI 影音工具站 - 系統</title>
+    <link rel="icon" href="app.png" type="image/png">
+    <link rel="shortcut icon" href="app.png" type="image/png">
     <style>
         :root {
             --bg-color: #0b0c10;

docs/index_en.html

@@ -5,6 +5,8 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Studio0808 AI Video Tools - System</title>
+    <link rel="icon" href="app.png" type="image/png">
+    <link rel="shortcut icon" href="app.png" type="image/png">
     <style>
         :root {
             --bg-color: #0b0c10;