Download badge and boss sprite images locally during export

The seed export command now downloads badge images and boss sprites
from remote URLs and stores them in frontend/public/, rewriting the
JSON URLs to local paths. Sprites are namespaced by game version
(e.g. /boss-sprites/red/brock.png) so each generation can have
its own sprite style.

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

backend/src/app/seeds/run.py

@@ -1,6 +1,8 @@
 """Seed runner — reads JSON files and upserts into the database."""
 
 import json
+import re
+import urllib.request
 from pathlib import Path
 
 from sqlalchemy import func, select
@@ -403,11 +405,58 @@ async def _export_routes(session: AsyncSession, vg_data: dict):
     print(f"Routes: {exported} game files exported")
 
 
+FRONTEND_PUBLIC = Path(__file__).resolve().parents[4] / "frontend" / "public"
+
+
+def _slugify(name: str) -> str:
+    """Convert a name to a filename-safe slug: lowercase, hyphens, no special chars."""
+    slug = name.lower().replace(" ", "-")
+    slug = re.sub(r"[^a-z0-9-]", "", slug)
+    return slug
+
+
+def _download_image(
+    url: str,
+    output_dir: Path,
+    slug: str,
+    downloaded: set[str],
+) -> str:
+    """Download an image to output_dir/slug.ext if not already downloaded.
+
+    Returns the local path (relative to frontend/public).
+    """
+    url_ext = url.rsplit(".", 1)[-1].split("?")[0].lower()
+    if url_ext in ("png", "jpg", "jpeg", "gif", "webp", "svg"):
+        ext = f".{url_ext}"
+    else:
+        ext = ".png"
+
+    filename = f"{slug}{ext}"
+    dest = output_dir / filename
+
+    if filename not in downloaded:
+        output_dir.mkdir(parents=True, exist_ok=True)
+        req = urllib.request.Request(url, headers={"User-Agent": "nuzlocke-tracker/1.0"})
+        try:
+            with urllib.request.urlopen(req, timeout=30) as resp:
+                dest.write_bytes(resp.read())
+        except (urllib.error.URLError, OSError) as exc:
+            print(f"  Warning: failed to download {url}: {exc}")
+            return url
+        downloaded.add(filename)
+        print(f"  Downloaded: {dest.relative_to(FRONTEND_PUBLIC)}")
+
+    return f"/{dest.relative_to(FRONTEND_PUBLIC)}"
+
+
 async def _export_bosses(session: AsyncSession, vg_data: dict):
     """Export boss battles per version group."""
     vg_result = await session.execute(select(VersionGroup))
     slug_to_vg = {vg.slug: vg for vg in vg_result.scalars().all()}
 
+    badge_dir = FRONTEND_PUBLIC / "badges"
+    downloaded_badges: set[str] = set()
+
     exported = 0
     for vg_slug, vg_info in vg_data.items():
         vg = slug_to_vg.get(vg_slug)
@@ -429,19 +478,37 @@ async def _export_bosses(session: AsyncSession, vg_data: dict):
             continue
 
         first_game_slug = list(vg_info["games"].keys())[0]
-        data = [
-            {
+        sprite_dir = FRONTEND_PUBLIC / "boss-sprites" / first_game_slug
+        downloaded_sprites: set[str] = set()
+        data = []
+        for b in bosses:
+            badge_image_url = b.badge_image_url
+            sprite_url = b.sprite_url
+
+            if badge_image_url and b.badge_name:
+                badge_slug = _slugify(b.badge_name)
+                badge_image_url = _download_image(
+                    badge_image_url, badge_dir, badge_slug, downloaded_badges,
+                )
+
+            if sprite_url:
+                sprite_slug = _slugify(b.name)
+                sprite_url = _download_image(
+                    sprite_url, sprite_dir, sprite_slug, downloaded_sprites,
+                )
+
+            data.append({
                 "name": b.name,
                 "boss_type": b.boss_type,
                 "specialty_type": b.specialty_type,
                 "badge_name": b.badge_name,
-                "badge_image_url": b.badge_image_url,
+                "badge_image_url": badge_image_url,
                 "level_cap": b.level_cap,
                 "order": b.order,
                 "after_route_name": b.after_route.name if b.after_route else None,
                 "location": b.location,
                 "section": b.section,
-                "sprite_url": b.sprite_url,
+                "sprite_url": sprite_url,
                 "pokemon": [
                     {
                         "pokeapi_id": bp.pokemon.pokeapi_id,
@@ -451,9 +518,7 @@ async def _export_bosses(session: AsyncSession, vg_data: dict):
                     }
                     for bp in sorted(b.pokemon, key=lambda p: p.order)
                 ],
-            }
-            for b in bosses
-        ]
+            })
 
         _write_json(f"{first_game_slug}-bosses.json", data)
         exported += 1