feat(UI-Overhaul-Phase7): Reports UI mit ResizablePanel und PluginToolbar

Migration 0139: Add folder_id column to report_templates for folder-based organization

Backend:
- ReportTemplate model: add folder_id field (nullable UUID)

Frontend:
- api/reports.ts: ReportTemplate interface updated with folder_id
- Reports.tsx: Added ResizablePanel for template list (resizable left sidebar)
- Reports.tsx: Added PluginToolbar registration with new-report button
- Reports.tsx: Added useEffect import for toolbar registration

tsc clean

alembic/versions/0139_reports_folder_id.py

@@ -0,0 +1,28 @@
+"""Reports: folder_id column for folder-based sorting
+
+Revision ID: 0139
+Revises: 0138
+Create Date: 2026-08-21
+
+Adds folder_id to report_templates for folder-based organization.
+"""
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import UUID as PGUUID
+
+# revision identifiers, used by Alembic.
+revision = "0139"
+down_revision = "0138"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("report_templates", sa.Column("folder_id", PGUUID(as_uuid=True), nullable=True))
+    op.create_index("ix_report_templates_folder", "report_templates", ["folder_id"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_report_templates_folder", table_name="report_templates")
+    op.drop_column("report_templates", "folder_id")