Add tag editing and PDF preview to documents feature

Each document's tags are now editable inline: click Edit to enter a tag
editor (Enter/comma to add, × to remove, Save to persist). The View
button opens the PDF in a new browser tab via blob URL. Both features
work through the existing proxy — no proxy changes needed.

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

features/doc-service/app/routers/documents.py

@@ -16,7 +16,7 @@ from app.deps import get_user_id
 from app.models.category import DocumentCategory
 from app.models.category_assignment import CategoryAssignment
 from app.models.document import Document
-from app.schemas.document import DocumentOut, DocumentStatusOut, DocumentTypeUpdate
+from app.schemas.document import DocumentOut, DocumentStatusOut, DocumentTypeUpdate, TagsUpdate
 from app.services.ai_client import AIServiceError, classify_document
 from app.services.config_reader import load_doc_config
 from app.services.storage import delete_file, get_upload_path, save_upload
@@ -205,6 +205,28 @@ async def update_document_type(
     return _doc_with_categories(doc)
 
 
+@router.patch("/{doc_id}/tags", response_model=DocumentOut)
+async def update_document_tags(
+    doc_id: str,
+    body: TagsUpdate,
+    user_id: str = Depends(get_user_id),
+    db: AsyncSession = Depends(get_db),
+) -> DocumentOut:
+    doc = await _get_user_doc(doc_id, user_id, db)
+    # Normalise: strip whitespace, drop empties, deduplicate while preserving order
+    seen: set[str] = set()
+    clean: list[str] = []
+    for t in body.tags:
+        t = t.strip()
+        if t and t.lower() not in seen:
+            seen.add(t.lower())
+            clean.append(t)
+    doc.tags = json.dumps(clean)
+    await db.commit()
+    doc = await _get_user_doc(doc_id, user_id, db)
+    return _doc_with_categories(doc)
+
+
 @router.delete("/{doc_id}", status_code=204)
 async def delete_document(
     doc_id: str,