feat: APK distribution pipeline — server hosting + Pi auto-update + /app routes

templates/app.html

@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<html data-bs-theme="light" lang="en">
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no">
+    <title>Install — Yaris OBD</title>
+    <link rel="stylesheet" href="{{ url_for('static', filename='bootstrap/css/bootstrap.min.css') }}">
+    <link rel="stylesheet" href="{{ url_for('static', filename='yaris.css') }}">
+</head>
+<body class="bg-light d-flex align-items-center justify-content-center" style="min-height:100vh;">
+    <div class="card shadow-sm p-4" style="width:100%;max-width:420px;">
+        <div class="text-center mb-3">
+            <span class="sidebar-brand-logo" style="color:#1c1c1e;">YARIS-OBD</span>
+            <div class="badge bg-warning text-dark mt-1">Android companion</div>
+        </div>
+        {% if apk_exists %}
+        <a class="btn btn-primary w-100 btn-lg" href="{{ url_for('app_download_apk') }}">
+            <i class="fas fa-download me-1"></i>Download yaris-obd.apk
+        </a>
+        <p class="text-muted small text-center mt-2">
+            {{ (apk_size / 1024 / 1024) | round(1) }} MB — after downloading, open the
+            file and enable "Install unknown apps" for your browser if prompted.
+        </p>
+        {% else %}
+        <div class="alert alert-warning mb-0">
+            The APK hasn't been mirrored yet. The Pi downloads it from the server
+            automatically when it has internet — try again shortly.
+        </div>
+        {% endif %}
+    </div>
+</body>
+</html>