Redesign doc service UX for scale + add group-based document sharing

- Three-column layout: Sidebar + SourcePanel (views + searchable category tree) + main
- DocumentSlideOver (480px right panel): inline editing, type picker, AI suggestion confirm/reject,
  categories combobox, tags editor, sharing section, raw text, re-analyse/delete actions
- ManageCategoriesDialog: inline rename, delete with confirm, search filter
- DocumentsPage rewrite: filter chip system, multi-file upload queue, drag-and-drop overlay,
  bulk actions bar (share/delete), smart TanStack Query polling, URL-driven view state
- Sidebar simplified: per-category NavLinks removed; Documents = single NavLink under Apps
- Backend: document_shares table (migration 0004), share CRUD endpoints, shared-with-me view,
  N+1-safe share_count via GROUP BY, recipient download access, X-User-Groups header enforcement
- Gateway proxy: injects X-User-Groups header into all document + category proxy requests
- Backend users: GET /api/users/me/groups endpoint for share picker combobox
- CLAUDE.md, STATUS.md files, and changelog updated

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

features/doc-service/app/models/__init__.py

@@ -1,5 +1,6 @@
 from app.models.document import Document
 from app.models.category import DocumentCategory
 from app.models.category_assignment import CategoryAssignment
+from app.models.document_share import DocumentShare
 
-__all__ = ["Document", "DocumentCategory", "CategoryAssignment"]
+__all__ = ["Document", "DocumentCategory", "CategoryAssignment", "DocumentShare"]

features/doc-service/app/models/document_share.py

@@ -0,0 +1,23 @@
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, String, UniqueConstraint, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+
+class DocumentShare(Base):
+    __tablename__ = "document_shares"
+
+    id: Mapped[str] = mapped_column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
+    document_id: Mapped[str] = mapped_column(String, nullable=False, index=True)
+    group_id: Mapped[str] = mapped_column(String, nullable=False, index=True)
+    shared_by_user_id: Mapped[str] = mapped_column(String, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), nullable=False
+    )
+
+    __table_args__ = (
+        UniqueConstraint("document_id", "group_id", name="uq_document_group_share"),
+    )