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/alembic/versions/0004_add_document_shares.py

@@ -0,0 +1,42 @@
+"""add document_shares table
+
+Revision ID: 0004
+Revises: 0003
+Create Date: 2026-04-18
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0004"
+down_revision: Union[str, None] = "0003"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "document_shares",
+        sa.Column("id", sa.String(), nullable=False),
+        sa.Column("document_id", sa.String(), nullable=False),
+        sa.Column("group_id", sa.String(), nullable=False),
+        sa.Column("shared_by_user_id", sa.String(), nullable=False),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.text("now()"),
+            nullable=False,
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint("document_id", "group_id", name="uq_document_group_share"),
+    )
+    op.create_index("ix_document_shares_document_id", "document_shares", ["document_id"])
+    op.create_index("ix_document_shares_group_id", "document_shares", ["group_id"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_document_shares_group_id", table_name="document_shares")
+    op.drop_index("ix_document_shares_document_id", table_name="document_shares")
+    op.drop_table("document_shares")