feat(sources): PDF-Upload als neuer Quellentyp pdf_document

- POST /api/sources/global/upload-pdf: multipart File-Upload,
  50 MB Limit, SHA256-Dedup, speichert PDF unter <dirname(DB)>/pdfs/{sha}.pdf,
  legt Source mit processed_at=NULL an (Monitor verarbeitet asynchron)
- pattern in GlobalSourceUpdate um pdf_document erweitert (2x)
- dashboard.html: Button + Modal im Grundquellen-Sub-Tab
- sources.js: openPdfUploadModal + setupPdfUploadForm + FormData-Submit
- app.js: API.upload(path, formData) Helper fuer multipart
- requirements.txt: pypdf (Validierung optional)

src/static/dashboard.html

@@ -328,6 +328,7 @@
             <span class="text-secondary" id="globalSourceCount"></span>
           </div>
           <button class="btn btn-secondary" id="discoverSourceBtn">Erkennen</button>
+          <button class="btn btn-secondary" id="newPdfSourceBtn" style="margin-right:8px;">+ PDF hochladen</button>
           <button class="btn btn-primary" id="newGlobalSourceBtn">+ Neue Grundquelle</button>
         </div>
         <div class="card">
@@ -641,6 +642,7 @@
                 <option value="telegram_channel">Telegram-Kanal</option>
                 <option value="podcast_feed">Podcast-Feed</option>
                 <option value="excluded">Ausgeschlossen</option>
+                <option value="pdf_document" disabled>PDF-Dokument (nur Upload)</option>
               </select>
             </div>
             <div class="form-group">
@@ -799,6 +801,59 @@
     </div>
   </div>
 
+  <!-- Modal: PDF hochladen -->
+  <div class="modal-overlay" id="modalPdfUpload">
+    <div class="modal">
+      <div class="modal-header">
+        <h3>PDF als Quelle hochladen</h3>
+        <button class="modal-close" onclick="closeModal(modalPdfUpload)">&times;</button>
+      </div>
+      <form id="pdfUploadForm" enctype="multipart/form-data">
+        <div class="modal-body">
+          <p class="text-secondary" style="margin-top:0;">
+            Die PDF wird gespeichert und vom Monitor automatisch verarbeitet:
+            Text extrahieren (OCR-Fallback fuer gescannte Dokumente),
+            Übersetzung nach Deutsch und Englisch.
+          </p>
+          <div class="form-group">
+            <label for="pdfFile">PDF-Datei (max. 50 MB)</label>
+            <input type="file" id="pdfFile" accept="application/pdf,.pdf" required>
+          </div>
+          <div class="form-group">
+            <label for="pdfName">Anzeige-Name (optional)</label>
+            <input type="text" id="pdfName" maxlength="200" placeholder="leer = Dateiname">
+          </div>
+          <div style="display:grid;grid-template-columns:1fr 1fr;gap:12px;">
+            <div class="form-group">
+              <label for="pdfCategory">Kategorie</label>
+              <select id="pdfCategory">
+                <option value="sonstige" selected>Sonstige</option>
+                <option value="behoerde">Behörde</option>
+                <option value="think-tank">Think-Tank</option>
+                <option value="fachmedien">Fachmedien</option>
+                <option value="international">International</option>
+              </select>
+            </div>
+            <div class="form-group">
+              <label for="pdfLanguage">Sprache (optional)</label>
+              <input type="text" id="pdfLanguage" list="languageSuggestions" placeholder="z.B. Deutsch, Englisch">
+            </div>
+          </div>
+          <div class="form-group">
+            <label for="pdfNotes">Notizen</label>
+            <input type="text" id="pdfNotes" placeholder="Optional">
+          </div>
+          <div id="pdfUploadError" class="error-msg" style="display:none"></div>
+          <div id="pdfUploadProgress" class="text-secondary" style="display:none;margin-top:8px;">Lädt hoch …</div>
+        </div>
+        <div class="modal-footer">
+          <button type="button" class="btn btn-secondary" onclick="closeModal(modalPdfUpload)">Abbrechen</button>
+          <button type="submit" class="btn btn-primary" id="pdfUploadSubmitBtn">Hochladen</button>
+        </div>
+      </form>
+    </div>
+  </div>
+
   <!-- Modal: Discover Sources -->
   <div class="modal-overlay" id="modalDiscover">
     <div class="modal" style="max-width:600px;">