fix: rename existing system categories to PascalCase-with-dashes via migration

Migration 0007 converts all scope='system' category names in-place
(e.g. "invoices" → "Invoices", "vendor-invoices" → "Vendor-Invoices").

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

features/doc-service/CLAUDE.md

@@ -117,6 +117,7 @@ Unique constraint: `(document_id, group_id)`
 | `0004` | `add_document_shares` |
 | `0005` | `add_share_can_delete` |
 | `0006` | `add_category_scope` |
+| `0007` | `capitalize_system_category_names` |
 
 ---
 

features/doc-service/alembic/versions/0007_capitalize_system_category_names.py

@@ -0,0 +1,44 @@
+"""capitalize existing system category names to PascalCase-with-dashes
+
+Revision ID: 0007
+Revises: 0006
+Create Date: 2026-04-18
+
+Converts names like "invoices" → "Invoices", "vendor-invoices" → "Vendor-Invoices"
+for all categories with scope='system' (watch-ingested).
+"""
+from typing import Sequence, Union
+
+import re
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy import text
+
+
+revision: str = "0007"
+down_revision: Union[str, None] = "0006"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def _to_pascal(name: str) -> str:
+    return "-".join(p.capitalize() for p in re.split(r"[-_\s]+", name) if p)
+
+
+def upgrade() -> None:
+    conn = op.get_bind()
+    rows = conn.execute(
+        text("SELECT id, name FROM document_categories WHERE scope = 'system'")
+    ).fetchall()
+    for row in rows:
+        new_name = _to_pascal(row.name)
+        if new_name != row.name:
+            conn.execute(
+                text("UPDATE document_categories SET name = :name WHERE id = :id"),
+                {"name": new_name[:128], "id": row.id},
+            )
+
+
+def downgrade() -> None:
+    pass  # names before migration are unknown; downgrade is a no-op