Dashboard account section, profile API, and CSS account panels

- SSO session auth gating on all protected pages
- dashboard.php: account section (profile form + workspace panel),
  onboarding prompt modal, overview bar extracted to CSS classes,
  dashboard.css linked in page head
- api/profile.php: save/dismiss endpoint for optional profile fields
- assets/css/dashboard.css: account grid, dash-account-panel,
  dash-profile-form, profile-prompt-backdrop modal, overview bar
  classes, dash-section-kicker, dash-tier-badge base styles
- includes/bootstrap.php: dbnToolsMainUserProfile,
  dbnToolsProfileNeedsPrompt, dbnToolsRequirePageAuth
- scripts/sql/004_user_profile_fields.sql: nullable phone, address,
  and profile_prompt_dismissed_at columns

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

includes/nav.php

@@ -13,7 +13,7 @@ $_navLang    = dbnToolsCurrentLanguage();
 $_navTools   = dbnToolsLaunchedTools($_navLang);
 $_navPath    = strtok((string)($_SERVER['REQUEST_URI'] ?? '/'), '?') ?: '/';
 $_navOnDash  = str_starts_with($_navPath, '/dashboard');
-$_navReturnUrl = urlencode($_navPath);
+$_navLoginUrl = dbnToolsMainLoginUrl($_navPath);
 $_navScriptPath = str_replace('\\', '/', (string)($_SERVER['SCRIPT_NAME'] ?? ''));
 $_navAssetBase = str_contains($_navScriptPath, '/dashboard/') ? '../assets' : 'assets';
 ?>
@@ -84,11 +84,11 @@ $_navAssetBase = str_contains($_navScriptPath, '/dashboard/') ? '../assets' : 'a
         </nav>
 
 <?php if ($_navGuest): ?>
-        <a href="/?return=<?= $_navReturnUrl ?>" class="dbn-nav__login">
+        <a href="<?= htmlspecialchars($_navLoginUrl) ?>" class="dbn-nav__login">
             <?= htmlspecialchars(dbnToolsT('nav_login', $_navLang)) ?>
         </a>
 <?php else: ?>
-        <a class="dbn-nav__account-link" href="/account.php" title="<?= htmlspecialchars($_navEmail) ?>">
+        <a class="dbn-nav__account-link" href="/dashboard.php#account" title="<?= htmlspecialchars($_navEmail) ?>">
 <?php if ($_navUser !== ''): ?>
             <span class="dbn-nav__username"><?= htmlspecialchars($_navUser) ?></span>
 <?php endif; ?>