Add dynamic variable support to Assistant model and related components

- Introduce dynamic variable definitions in AssistantConfig and Assistant models, allowing for flexible prompt customization.
- Implement validation for dynamic variable names and types in the schema.
- Update backend services and routes to handle dynamic variables in assistant configurations and runtime processing.
- Enhance frontend components to support dynamic variable definitions, including a new editor for managing variables.
- Add tests to ensure proper functionality and validation of dynamic variables in various scenarios.

backend/migrations/versions/20260712_0007_add_dynamic_variables.py

@@ -0,0 +1,30 @@
+"""add assistant dynamic variable definitions
+
+Revision ID: 20260712_0007
+Revises: 20260712_0006
+"""
+from collections.abc import Sequence
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = "20260712_0007"
+down_revision: str | Sequence[str] | None = "20260712_0006"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "assistants",
+        sa.Column(
+            "dynamic_variable_definitions",
+            sa.JSON(),
+            server_default=sa.text("'{}'"),
+            nullable=False,
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("assistants", "dynamic_variable_definitions")