Fix Bedrock advocate synthesis: engine guard, response_format, Claude engine option

- DeepResearchAgent: engine guard now accepts dbn_legal_v3, claude_sonnet, claude_haiku
  (previously stripped these to azure_mini, breaking dbn_legal_v3 selection and
  preventing Claude engines from reaching the correct synthesis branch)
- DbnBedrockGateway: remove response_format=json_object from chat payload — LiteLLM
  converts this to a tool-use constraint for Bedrock, routing output into tool_calls
  instead of content (root cause of the {} empty brief)
- advocate.php: add Claude Sonnet 4.6 (AWS Bedrock) engine option
- account, billing, dashboard, nav, min-sak: pending UI/flow changes from prior sessions

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

includes/DbnBedrockGateway.php

@@ -96,9 +96,10 @@ final class DbnBedrockGateway
             'temperature' => (float)($options['temperature'] ?? 0.2),
             'max_tokens'  => $options['max_tokens'] ?? 1200,
         ];
-        if (!empty($options['json'])) {
-            $payload['response_format'] = ['type' => 'json_object'];
-        }
+        // response_format is intentionally omitted for Claude via Bedrock.
+        // LiteLLM converts json_object to a tool-use constraint, routing output
+        // into tool_calls instead of content. Claude follows JSON instructions
+        // in the system prompt without needing response_format.
 
         return $this->postJson($this->liteLlmUrl, $payload, (int)($options['timeout'] ?? 90));
     }

includes/DeepResearchAgent.php

@@ -40,7 +40,7 @@ final class DbnDeepResearchAgent
     ): array {
         $seedQuery   = trim($seedQuery);
         $pastedText  = trim($pastedText);
-        $engine      = in_array($engine, ['azure_mini', 'azure_full', 'gpu'], true) ? $engine : 'azure_mini';
+        $engine      = in_array($engine, ['azure_mini', 'azure_full', 'gpu', 'dbn_legal', 'dbn_legal_v3', 'claude_sonnet', 'claude_haiku'], true) ? $engine : 'azure_mini';
         $language    = dbnToolsNormalizeUiLanguage($language);
 
         $controls = $this->normalizeControls($controls);
@@ -1221,7 +1221,7 @@ PROMPT;
     ): array {
         $seedQuery  = trim($seedQuery);
         $pastedText = trim($pastedText);
-        $engine     = in_array($engine, ['azure_mini', 'azure_full', 'gpu'], true) ? $engine : 'azure_mini';
+        $engine     = in_array($engine, ['azure_mini', 'azure_full', 'gpu', 'dbn_legal', 'dbn_legal_v3', 'claude_sonnet', 'claude_haiku'], true) ? $engine : 'azure_mini';
         $language   = dbnToolsNormalizeUiLanguage($language);
         $controls   = $this->normalizeControls($controls);
 

includes/nav.php

@@ -88,7 +88,7 @@ $_navAssetBase = str_contains($_navScriptPath, '/dashboard/') ? '../assets' : 'a
             <?= htmlspecialchars(dbnToolsT('nav_login', $_navLang)) ?>
         </a>
 <?php else: ?>
-        <a class="dbn-nav__account-link" href="/dashboard.php#account" title="<?= htmlspecialchars($_navEmail) ?>">
+        <a class="dbn-nav__account-link" href="/account.php" title="<?= htmlspecialchars($_navEmail) ?>">
 <?php if ($_navUser !== ''): ?>
             <span class="dbn-nav__username"><?= htmlspecialchars($_navUser) ?></span>
 <?php endif; ?>