Add Google Analytics tracking to all pages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sovanesyan

docs/index.html

@@ -6,6 +6,8 @@
   <title>Calendarchy — Terminal Calendar</title>
   <meta name="description" content="A keyboard first calendar TUI.">
   <link rel="icon" type="image/svg+xml" href="favicon.svg">
+  <script async src="https://www.googletagmanager.com/gtag/js?id=G-RE3XJ4NKTF"></script>
+  <script>window.dataLayer=window.dataLayer||[];function gtag(){dataLayer.push(arguments);}gtag('js',new Date());gtag('config','G-RE3XJ4NKTF');</script>
   <style>
     @font-face {
       font-display: swap;

docs/privacy.html

@@ -4,6 +4,8 @@
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>Privacy Policy — Calendarchy</title>
+  <script async src="https://www.googletagmanager.com/gtag/js?id=G-RE3XJ4NKTF"></script>
+  <script>window.dataLayer=window.dataLayer||[];function gtag(){dataLayer.push(arguments);}gtag('js',new Date());gtag('config','G-RE3XJ4NKTF');</script>
   <style>
     :root {
       --bg: #0e0e12;

docs/terms.html

@@ -4,6 +4,8 @@
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>Terms of Service — Calendarchy</title>
+  <script async src="https://www.googletagmanager.com/gtag/js?id=G-RE3XJ4NKTF"></script>
+  <script>window.dataLayer=window.dataLayer||[];function gtag(){dataLayer.push(arguments);}gtag('js',new Date());gtag('config','G-RE3XJ4NKTF');</script>
   <style>
     :root {
       --bg: #0e0e12;