Add per-condition encounter rates to seed data

Add a `condition` column to RouteEncounter so encounters can store
per-condition rates (time of day, season, weather) instead of flattening
to max(). Update the seed loader, API schemas, and frontend to support
the new `conditions` dict format in seed JSON.

Port the PoC branch's condition-aware EncounterModal UI with filter
tabs that let players see encounter rates for specific conditions.
Add horde/SOS as distinct encounter methods with their own badges.

Update the import tool to extract per-condition rates instead of
flattening, and add a merge script (tools/merge-conditions.py) that
enriches existing curated seed files with condition data from PokeDB.

Seed data updated for 22 games (5,684 encounters):
- Gen 2: Gold, Silver, Crystal (morning/day/night)
- Gen 4: HG, SS, Diamond, Pearl, Platinum, BD, SP (morning/day/night)
- Gen 5: Black, White, Black 2, White 2 (spring/summer/autumn/winter)
- Gen 7: Sun, Moon, Ultra Sun, Ultra Moon (day/night)
- Gen 8: Sword, Shield (weather)

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

tools/import-pokedb/import_pokedb/models.py

@@ -13,16 +13,22 @@ class Encounter:
     encounter_rate: int
     min_level: int
     max_level: int
+    conditions: dict[str, int] | None = None
 
     def to_dict(self) -> dict:
-        return {
+        d: dict = {
             "pokeapi_id": self.pokeapi_id,
             "pokemon_name": self.pokemon_name,
             "method": self.method,
-            "encounter_rate": self.encounter_rate,
             "min_level": self.min_level,
             "max_level": self.max_level,
         }
+        if self.conditions:
+            d["encounter_rate"] = None
+            d["conditions"] = self.conditions
+        else:
+            d["encounter_rate"] = self.encounter_rate
+        return d
 
 
 @dataclass