Add after_route_name to boss battle export/seed pipeline

Exports now include after_route_name (resolved from the route FK),
and the seed loader resolves it back to an ID on import. Also adds
a draft bean for displaying encounter-less locations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/app/seeds/loader.py

@@ -211,10 +211,19 @@ async def upsert_bosses(
     version_group_id: int,
     bosses: list[dict],
     dex_to_id: dict[int, int],
+    route_name_to_id: dict[str, int] | None = None,
 ) -> int:
     """Upsert boss battles for a version group, return count of bosses upserted."""
     count = 0
     for boss in bosses:
+        # Resolve after_route_name to an ID
+        after_route_id = None
+        after_route_name = boss.get("after_route_name")
+        if after_route_name and route_name_to_id:
+            after_route_id = route_name_to_id.get(after_route_name)
+            if after_route_id is None:
+                print(f"  Warning: route '{after_route_name}' not found for boss '{boss['name']}'")
+
         # Upsert the boss battle on (version_group_id, order) conflict
         stmt = insert(BossBattle).values(
             version_group_id=version_group_id,
@@ -225,6 +234,7 @@ async def upsert_bosses(
             badge_image_url=boss.get("badge_image_url"),
             level_cap=boss["level_cap"],
             order=boss["order"],
+            after_route_id=after_route_id,
             location=boss["location"],
             section=boss.get("section"),
             sprite_url=boss.get("sprite_url"),
@@ -237,6 +247,7 @@ async def upsert_bosses(
                 "badge_name": boss.get("badge_name"),
                 "badge_image_url": boss.get("badge_image_url"),
                 "level_cap": boss["level_cap"],
+                "after_route_id": after_route_id,
                 "location": boss["location"],
                 "section": boss.get("section"),
                 "sprite_url": boss.get("sprite_url"),