v4.0.2: Add Web UI authentication and optional HTTPS

- Add single-admin login with SQLite3 user storage
- First-run setup wizard for admin account creation
- Account management page for password changes
- Optional HTTPS with auto-generated self-signed certificates
- Configurable via STEGASOO_AUTH_ENABLED, STEGASOO_HTTPS_ENABLED env vars
- UI improvements: larger QR previews, consistent panel styling
- Update docker-compose.yml with auth config and persistent volumes
- Update all documentation for v4.0.2

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontends/web/templates/encode.html

@@ -394,11 +394,11 @@
 
                     <!-- PIN + Channel Row -->
                     <div class="row">
-                        <div class="col-md-4 mb-3">
+                        <div class="col-md-6 mb-3">
                           <div class="security-box h-100">
                             <label class="form-label"><i class="bi bi-123 me-1"></i> PIN</label>
                             <div class="input-group pin-input-container">
-                              <input type="password" name="pin" class="form-control" id="pinInput" placeholder="••••••" maxlength="9" style="max-width: 180px;">
+                              <input type="password" name="pin" class="form-control" id="pinInput" placeholder="••••••" maxlength="9">
                               <button class="btn btn-outline-secondary" type="button" data-toggle-password="pinInput">
                                 <i class="bi bi-eye"></i>
                               </button>
@@ -407,7 +407,7 @@
                           </div>
                         </div>
 
-                        <div class="col-md-8 mb-3">
+                        <div class="col-md-6 mb-3">
                           <div class="security-box h-100">
                             <label class="form-label">
                                 <i class="bi bi-broadcast me-1"></i> Channel