feat(dashboard): streamlit skeleton + Overview page + data layer

Aggiunge scheletro multipage Streamlit per Phase 1:
- modulo data.py con helper (list_runs_df, get_run_overview,
  generations_df, evaluations_df, genomes_df) sopra Repository.
- streamlit_app.py entry point con DB_PATH da env.
- pages/01_overview.py per elenco run + metriche + config JSON.
- smoke test import di multi_swarm.dashboard.data.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/integration/test_streamlit_smoke.py

@@ -0,0 +1,14 @@
+import importlib
+
+
+def test_streamlit_app_imports():
+    importlib.import_module("multi_swarm.dashboard.data")
+
+
+def test_dashboard_data_helpers_signatures():
+    from multi_swarm.dashboard import data
+
+    assert hasattr(data, "list_runs_df")
+    assert hasattr(data, "generations_df")
+    assert hasattr(data, "evaluations_df")
+    assert hasattr(data, "genomes_df")