feat(api): add INCI tool-calling with normalized tool traces

Enable on-demand INCI retrieval in /routines/suggest through Gemini function calling so detailed ingredient data is fetched only when needed. Persist and normalize tool_trace data in AI logs to make function-call behavior directly inspectable via /ai-logs endpoints.

backend/alembic/versions/d3e4f5a6b7c8_add_tool_trace_to_ai_call_logs.py

@@ -0,0 +1,29 @@
+"""add_tool_trace_to_ai_call_logs
+
+Revision ID: d3e4f5a6b7c8
+Revises: b2c3d4e5f6a1
+Create Date: 2026-03-04 00:00:00.000000
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+
+from alembic import op
+
+revision: str = "d3e4f5a6b7c8"
+down_revision: Union[str, None] = "b2c3d4e5f6a1"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "ai_call_logs",
+        sa.Column("tool_trace", sa.JSON(), nullable=True),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("ai_call_logs", "tool_trace")