feat: portage complet en Rust (axum + sysinfo + tera)

Remplacement du backend Python/Flask par un binaire Rust natif.
Stack : axum (web), sysinfo (metriques), lettre (SMTP), tera (templates), argon2 (auth).
Binaire Windows 6.3 Mo sans dependance runtime.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/login.html

@@ -23,20 +23,18 @@
                 <small class="text-secondary">Monitoring systeme</small>
             </div>
 
-            {% with messages = get_flashed_messages(with_categories=true) %}
-            {% if messages %}
-                {% for category, message in messages %}
-                <div class="alert alert-{{ category }} alert-dismissible fade show" role="alert">
-                    {{ message }}
+            {% if flash_messages %}
+                {% for msg in flash_messages %}
+                <div class="alert alert-{{ msg.category }} alert-dismissible fade show" role="alert">
+                    {{ msg.message }}
                     <button type="button" class="btn-close" data-bs-dismiss="alert"></button>
                 </div>
                 {% endfor %}
             {% endif %}
-            {% endwith %}
 
             <div class="card shadow">
                 <div class="card-body p-4">
-                    <form method="POST" action="{{ url_for('login') }}">
+                    <form method="POST" action="/login">
                         <div class="mb-3">
                             <label for="username" class="form-label">Identifiant</label>
                             <div class="input-group">