v0.7.0: Phase 1 — Authentication, Persistence & Settings Page

- New settings.json persistence layer (internal/settings/settings.go)
  - Atomic write (tmp + rename), thread-safe with sync.RWMutex
  - Stores password hash overrides and DB validation cache
  - Auto-creates on first save, graceful handling if missing

- Auth improvements
  - Password resolution priority: settings.json > controller.yaml > none
  - Session duration extended to 7 days (was 24h)
  - ?next= redirect after session expiry (returns to original page)
  - Flash messages on login page (used after password change)
  - Conditional logout link (hidden when auth disabled)
  - Session invalidation on password change

- New Settings page (/settings)
  - Read-only system config display (customer, domain, git, backup, monitoring)
  - Password change form with validation (min 8 chars, match check)
  - Sidebar "Beállítások" item pinned to bottom above version

- DB validation persistence
  - Validation results saved to settings.json after each dump
  - Cached data survives container restarts

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

controller/internal/web/templates/login.html

@@ -11,8 +11,10 @@
     <div class="login-card">
         <img src="/static/felhom-logo.svg" alt="Felhom.eu" class="login-logo">
         <p class="login-subtitle">{{.CustomerName}}</p>
+        {{if .Flash}}<div class="alert alert-info">{{.Flash}}</div>{{end}}
         {{if .Error}}<div class="alert alert-error">{{.Error}}</div>{{end}}
         <form method="POST" action="/login">
+            <input type="hidden" name="next" id="next-field" value="">
             <div class="form-group">
                 <label for="password">Jelszó</label>
                 <input type="password" id="password" name="password" required autofocus
@@ -23,6 +25,15 @@
         <p class="login-footer">Felhom — Otthoni szerver kezelés<br>
         <a href="https://felhom.eu" target="_blank">felhom.eu</a></p>
     </div>
+    <script>
+    (function() {
+        var params = new URLSearchParams(window.location.search);
+        var next = params.get('next');
+        if (next) {
+            document.getElementById('next-field').value = next;
+        }
+    })();
+    </script>
 </body>
 </html>
 {{end}}