feat(sources): X-Account-Verwaltung im Verwaltungsportal

Neuer Sub-Tab "X-Accounts" unter Quellen: die als Recherchequelle
eingebundenen X-Accounts anzeigen, hinzufuegen, bearbeiten und entfernen.
Schreibt source_type=x_account in die geteilte sources-Tabelle, von wo
der Monitor sie pro Lage nutzt.

- x_account im source_type-Pattern von GlobalSourceCreate/Update
- primary_language in Create/Update plus INSERT (Keyword-Matching)
- x_account-Typ und x-Kategorie in source_meta.py
- Sub-Tab, Tabelle und Modal in dashboard.html, Logik in sources.js

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/static/dashboard.html

@@ -329,6 +329,7 @@
         <button class="nav-tab" data-subtab="tenant-sources">Kundenquellen</button>
         <button class="nav-tab" data-subtab="source-health">Quellen-Health</button>
         <button class="nav-tab" data-subtab="classification-review">Klassifikation <span class="sources-tab-badge" id="classificationPendingBadge">0</span></button>
+        <button class="nav-tab" data-subtab="x-accounts">X-Accounts</button>
       </div>
 
       <!-- Grundquellen -->
@@ -471,6 +472,36 @@
         </div>
       </div>
 
+      <!-- X-Accounts (Sub-Tab) -->
+      <div class="section" id="sub-x-accounts">
+        <div class="action-bar">
+          <div style="display:flex;align-items:center;gap:12px;flex-wrap:wrap;">
+            <input type="text" class="search-input" id="xAccountSearch" placeholder="X-Account suchen..." oninput="filterXAccounts()">
+            <span class="text-secondary" id="xAccountCount"></span>
+          </div>
+          <button class="btn btn-primary" id="newXAccountBtn" onclick="openXAccountModal()">+ X-Account hinzufügen</button>
+        </div>
+        <div class="card">
+          <p class="text-secondary" style="padding:0 4px 12px;">X-Accounts (Twitter), die der Monitor als Recherchequelle nutzt. Pro Lage über die Option „X (Twitter) einbeziehen" zuschaltbar.</p>
+          <div class="table-wrap">
+            <table>
+              <thead>
+                <tr>
+                  <th>Account</th>
+                  <th>URL</th>
+                  <th>Sprache</th>
+                  <th>Notiz</th>
+                  <th>Artikel</th>
+                  <th>Status</th>
+                  <th>Aktionen</th>
+                </tr>
+              </thead>
+              <tbody id="xAccountTable"></tbody>
+            </table>
+          </div>
+        </div>
+      </div>
+
     </div> <!-- /sec-sources -->
 
     <!-- Audit-Log Section -->
@@ -938,8 +969,59 @@
     </div>
   </div>
 
+  <!-- Modal: X-Account -->
+  <div class="modal-overlay" id="modalXAccount">
+    <div class="modal">
+      <div class="modal-header">
+        <h3 id="xAccountModalTitle">X-Account hinzufügen</h3>
+        <button class="modal-close" onclick="closeModal('modalXAccount')">&times;</button>
+      </div>
+      <form id="xAccountForm">
+        <div class="modal-body">
+          <div class="form-group">
+            <label for="xAccountHandle">X-Handle oder URL</label>
+            <input type="text" id="xAccountHandle" required placeholder="z.B. bellingcat oder https://x.com/bellingcat">
+            <small class="text-secondary">Account-Name mit oder ohne @, oder die volle x.com-URL.</small>
+          </div>
+          <div class="form-group">
+            <label for="xAccountName">Anzeigename</label>
+            <input type="text" id="xAccountName" placeholder="optional, z.B. Bellingcat">
+          </div>
+          <div class="form-group">
+            <label for="xAccountLanguage">Sprache</label>
+            <select id="xAccountLanguage">
+              <option value="en">Englisch</option>
+              <option value="de">Deutsch</option>
+              <option value="fr">Französisch</option>
+              <option value="ru">Russisch</option>
+              <option value="uk">Ukrainisch</option>
+              <option value="">Unbestimmt</option>
+            </select>
+            <small class="text-secondary">Steuert das Keyword-Matching im Monitor.</small>
+          </div>
+          <div class="form-group">
+            <label for="xAccountNotes">Notiz</label>
+            <textarea id="xAccountNotes" rows="2" placeholder="Kurzbeschreibung, hilft der KI bei der Account-Auswahl pro Lage"></textarea>
+          </div>
+          <div class="form-group">
+            <label for="xAccountStatus">Status</label>
+            <select id="xAccountStatus">
+              <option value="active">Aktiv</option>
+              <option value="inactive">Inaktiv</option>
+            </select>
+          </div>
+          <div id="xAccountError" class="error-msg" style="display:none"></div>
+        </div>
+        <div class="modal-footer">
+          <button type="button" class="btn btn-secondary" onclick="closeModal('modalXAccount')">Abbrechen</button>
+          <button type="submit" class="btn btn-primary">Speichern</button>
+        </div>
+      </form>
+    </div>
+  </div>
+
   <script src="/static/js/app.js?v=20260522a"></script>
-  <script src="/static/js/sources.js?v=20260509d"></script>
+  <script src="/static/js/sources.js?v=20260522x"></script>
   <script src="/static/js/source-health.js?v=20260509l"></script>
   <script src="/static/js/audit.js?v=20260509d"></script>
   <div id="toastContainer" class="toast-container" aria-live="polite" aria-atomic="true"></div>