fix: address reviewer feedback — dynamic sitemap/robots + wildcard CI branches

- CI workflow: replace hardcoded branch list with ['**'] wildcard so
  pipeline runs on every branch push, not just 4 named branches.

- Sitemap/robots.txt: moved from static files to dynamic generation.
  New sitemap_export.py module (follows theme_export.py pattern) uses
  KMTN_WEBSITE_URL to generate tenant-aware sitemap.xml and robots.txt
  on app startup. Atomic writes to STATIC_FILES_DIR so Nginx serves them.

- Added /api/sitemap endpoint with /status (public) and /regenerate
  (admin-only) for runtime control.

Addresses reviewer comments on PR #4:
  1. 'more general way to ensure this runs on any branch on push'
  2. 'whitelabel app - this file may need to be dynamically generated'

backend/app/main.py

@@ -10,7 +10,7 @@ from app.config import settings
 from app.database import async_session, engine
 from app.models import Base, Show, StationConfig, HistoryEntry, TeamMember, CommunityHighlight, Underwriter
 from app.user_models import User
-from app.api import events, auth, station_config, history, team, community, shows, storage, underwriters, stats, mobile_builds, theme
+from app.api import events, auth, station_config, history, team, community, shows, storage, underwriters, stats, mobile_builds, theme, sitemap
 
 
 def _cleanup_orphaned_sequences(sync_conn):
@@ -183,6 +183,14 @@ async def lifespan(app: FastAPI):
     except Exception as e:
         print(f"  WARNING: Failed to write theme.json on startup: {e}")
 
+    # Write sitemap.xml + robots.txt on startup (tenant-aware)
+    try:
+        from app.sitemap_export import write_sitemap_files
+        info = write_sitemap_files()
+        print(f"  ✓ Sitemap + robots.txt written (base_url={info['base_url']})")
+    except Exception as e:
+        print(f"  WARNING: Failed to write sitemap on startup: {e}")
+
     # Check GeoLite2 database
     geo_db = settings.GEOLITE2_DB_PATH
     if os.path.exists(geo_db):
@@ -235,6 +243,7 @@ app.include_router(underwriters.router, prefix="/api/underwriters", tags=["under
 app.include_router(stats.router, prefix="/api/stats", tags=["stats"])
 app.include_router(mobile_builds.router, prefix="/api/mobile-builds", tags=["mobile-builds"])
 app.include_router(theme.router, prefix="/api/theme", tags=["theme"])
+app.include_router(sitemap.router, prefix="/api/sitemap", tags=["sitemap"])
 
 # Admin user management (available in all environments)
 from app.api import users