Phase 15: language + bias als Spalten, Filter, Edit-Form

Bisher waren die DB-Felder sources.language und sources.bias zwar gepflegt
(254/275 Quellen mit bias, 254 mit language), aber in der Verwaltung nicht
sichtbar. Der Admin konnte nicht filtern oder editieren.

Backend (routers/sources.py)
- GlobalSourceCreate + GlobalSourceUpdate Pydantic-Modelle: language +
  bias als Optional[str] erweitert (max 100 / 500 Zeichen).
- SOURCE_UPDATE_COLUMNS: language + bias hinzu.
- INSERT in create_global_source: schreibt language + bias mit.
- Neuer Endpoint GET /api/sources/global/languages: distinct language-Werte
  fuer Frontend-Filter-Dropdown.

Frontend HTML (dashboard.html)
- Grundquellen-Filter-Bar: Sprachen-Dropdown ergaenzt.
- Grundquellen-Tabellenkopf: 2 neue Spalten Sprache (sortable) + Bias.
- modalSource: 2 neue Felder language (mit datalist Vorschlaegen) + bias.
- Kundenquellen-Filter-Bar: Sprachen-Dropdown.
- Kundenquellen-Tabellenkopf: Sprache (sortable) + Bias.

Frontend JS (sources.js)
- loadGlobalSources lädt /languages parallel zu /global + /global/stats,
  populiert beide Sprache-Dropdowns + datalist im Edit-Modal.
- renderGlobalSources: cols 11 -> 13, language+bias-Zellen
  (Bias mit Tooltip fuer Lang-Texte).
- filterGlobalSources: Sprache-Filter, Bias in Suche.
- editGlobalSource: language + bias laden.
- Form-Submit: language + bias mitgesendet.
- renderTenantSources: cols 8 -> 10, language+bias-Zellen.
- tenantFilters um language erweitert, applyTenantFilterAndSort prueft.

Cache-Buster ?v=20260509 (heute) bleibt - Tag wechselt erst morgen.

src/static/dashboard.html

@@ -313,6 +313,9 @@
               <option value="active">Aktiv</option>
               <option value="inactive">Inaktiv</option>
             </select>
+            <select class="filter-select" id="globalFilterLanguage" onchange="filterGlobalSources()">
+              <option value="">Alle Sprachen</option>
+            </select>
             <span class="text-secondary" id="globalSourceCount"></span>
           </div>
           <button class="btn btn-secondary" id="discoverSourceBtn">Erkennen</button>
@@ -330,6 +333,8 @@
                   <th class="sortable" data-sort="article_count" onclick="sortGlobalSources('article_count')">Artikel <span class="sort-icon"></span></th>
                   <th class="sortable" data-sort="articles_30d" onclick="sortGlobalSources('articles_30d')">Aktivität <span class="sort-icon"></span></th>
                   <th class="sortable" data-sort="tenant_excluded_count" onclick="sortGlobalSources('tenant_excluded_count')">Sperren <span class="sort-icon"></span></th>
+                  <th class="sortable" data-sort="language" onclick="sortGlobalSources('language')">Sprache <span class="sort-icon"></span></th>
+                  <th>Bias</th>
                   <th class="sortable" data-sort="last_seen_at" onclick="sortGlobalSources('last_seen_at')">Letzter Treffer <span class="sort-icon"></span></th>
                   <th class="sortable" data-sort="health_status" onclick="sortGlobalSources('health_status')">Health <span class="sort-icon"></span></th>
                   <th class="sortable" data-sort="status" onclick="sortGlobalSources('status')">Status <span class="sort-icon"></span></th>
@@ -356,6 +361,9 @@
             <select class="filter-select" id="tenantFilterOrg" onchange="filterTenantSources()">
               <option value="">Alle Organisationen</option>
             </select>
+            <select class="filter-select" id="tenantFilterLanguage" onchange="filterTenantSources()">
+              <option value="">Alle Sprachen</option>
+            </select>
             <span class="text-secondary" id="tenantSourceCount"></span>
           </div>
           <button class="btn btn-primary" id="tenantBulkPromoteBtn" disabled onclick="bulkPromoteSelected()">
@@ -373,6 +381,8 @@
                   <th class="sortable" data-sort="source_type" onclick="sortTenantSources('source_type')">Typ <span class="sort-icon"></span></th>
                   <th class="sortable" data-sort="category" onclick="sortTenantSources('category')">Kategorie <span class="sort-icon"></span></th>
                   <th class="sortable" data-sort="org_name" onclick="sortTenantSources('org_name')">Organisation <span class="sort-icon"></span></th>
+                  <th class="sortable" data-sort="language" onclick="sortTenantSources('language')">Sprache <span class="sort-icon"></span></th>
+                  <th>Bias</th>
                   <th>Hinzugefügt von</th>
                   <th>Aktionen</th>
                 </tr>
@@ -597,12 +607,23 @@
               </select>
             </div>
           </div>
+          <div style="display:grid;grid-template-columns:1fr 1fr;gap:12px;">
+            <div class="form-group">
+              <label for="sourceStatus">Status</label>
+              <select id="sourceStatus">
+                <option value="active">Aktiv</option>
+                <option value="inactive">Inaktiv</option>
+              </select>
+            </div>
+            <div class="form-group">
+              <label for="sourceLanguage">Sprache</label>
+              <input type="text" id="sourceLanguage" list="languageSuggestions" placeholder="z.B. Deutsch, Englisch, Russisch">
+              <datalist id="languageSuggestions"></datalist>
+            </div>
+          </div>
           <div class="form-group">
-            <label for="sourceStatus">Status</label>
-            <select id="sourceStatus">
-              <option value="active">Aktiv</option>
-              <option value="inactive">Inaktiv</option>
-            </select>
+            <label for="sourceBias">Bias / Einordnung</label>
+            <input type="text" id="sourceBias" placeholder="z.B. Nachrichtenagentur, faktenbasiert-neutral" maxlength="500">
           </div>
           <div class="form-group">
             <label for="sourceNotes">Notizen</label>