feat(rag): add database routing to geographic query templates

Add databases: ["oxigraph"] to 4 geographic templates to skip vector search:
- list_institutions_by_type_city
- list_institutions_by_type_region
- list_institutions_by_type_country
- list_institutions_in_city

Also add documentation explaining database routing configuration in _metadata.

data/sparql_templates.yaml

@@ -50,6 +50,29 @@ _metadata:
   #   ui_template:
   #     nl: "Gevonden: {{ count }} {{ institution_type_nl }} in {{ city }}."
   #     en: "Found: {{ count }} {{ institution_type_en }} in {{ city }}."
+  #
+  # Database Routing Configuration
+  # ==============================
+  # Each template can specify which databases to query via `databases` (list).
+  # This allows skipping unnecessary data sources for faster, deterministic results.
+  #
+  # Available databases:
+  #   - "oxigraph": SPARQL Knowledge Graph (deterministic, has coordinates)
+  #   - "qdrant": Vector search (probabilistic, semantic similarity)
+  #
+  # Examples:
+  #   databases: ["oxigraph", "qdrant"]  # Default: query both (backward compatible)
+  #   databases: ["oxigraph"]            # SPARQL only - skip vector search
+  #   databases: ["qdrant"]              # Vector only - for exploration queries
+  #
+  # Use ["oxigraph"] for:
+  #   - Geographic/map queries (Oxigraph has lat/lon coordinates)
+  #   - Factual queries with known schema (counts, lists by type)
+  #   - Deterministic results without vector noise
+  #
+  # Use ["qdrant"] for:
+  #   - Semantic exploration ("similar institutions to X")
+  #   - Free-text search without structured slots
   
 # Standard SPARQL prefixes used in all templates
 _prefixes: |
@@ -473,6 +496,7 @@ templates:
     description: "List heritage institutions of a specific type in a city"
     intent: ["geographic", "exploration"]
     response_modes: ["table", "map"]
+    databases: ["oxigraph"]  # Geographic query - Oxigraph has lat/lon coordinates
     ui_template:
       nl: "Gevonden: {{ result_count }} {{ institution_type_nl }} in {{ city }}."
       en: "Found: {{ result_count }} {{ institution_type_en }} in {{ city }}."
@@ -556,6 +580,7 @@ templates:
     description: "List heritage institutions of a specific type in a province/region"
     intent: ["geographic", "exploration"]
     response_modes: ["table", "map"]
+    databases: ["oxigraph"]  # Geographic query - Oxigraph has lat/lon coordinates
     ui_template:
       nl: "Gevonden: {{ result_count }} {{ institution_type_nl }} in {{ region }}."
       en: "Found: {{ result_count }} {{ institution_type_en }} in {{ region }}."
@@ -620,6 +645,7 @@ templates:
     description: "List heritage institutions of a specific type in a country"
     intent: ["geographic", "exploration"]
     response_modes: ["table", "map"]
+    databases: ["oxigraph"]  # Geographic query - Oxigraph has lat/lon coordinates
     ui_template:
       nl: "Gevonden: {{ result_count }} {{ institution_type_nl }} in {{ country }}."
       en: "Found: {{ result_count }} {{ institution_type_en }} in {{ country }}."
@@ -839,6 +865,7 @@ templates:
     description: "List all heritage institutions in a city"
     intent: ["geographic", "exploration"]
     response_modes: ["table", "map"]
+    databases: ["oxigraph"]  # Geographic query - Oxigraph has lat/lon coordinates
     ui_template:
       nl: "Gevonden: {{ result_count }} erfgoedinstellingen in {{ city }}."
       en: "Found: {{ result_count }} heritage institutions in {{ city }}."