Offline downloads, service worker, iOS audio unlock fix

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server.py

@@ -41,7 +41,7 @@ SESSION_DAYS = 90
 
 # Files the browser fetches without a session (home-screen icon and manifest).
 PUBLIC = {"/manifest.webmanifest": "application/manifest+json", "/icon-180.png": "image/png",
-          "/icon-192.png": "image/png", "/icon-512.png": "image/png"}
+          "/icon-192.png": "image/png", "/icon-512.png": "image/png", "/sw.js": "text/javascript"}
 
 # Only read-only endpoints needed for listening are reachable; admin commands/import are not.
 ALLOWED = [re.compile(p) for p in (
@@ -223,7 +223,7 @@ class Handler(BaseHTTPRequestHandler):
             return self.logout()
         if path in PUBLIC:
             with open(os.path.join(HERE, path[1:]), "rb") as f:
-                return self.send_body(200, f.read(), PUBLIC[path], [("Cache-Control", "public, max-age=86400")])
+                return self.send_body(200, f.read(), PUBLIC[path], [("Cache-Control", "no-cache" if path in ("/sw.js", "/manifest.webmanifest") else "public, max-age=86400")])
         user = self.user()
         if not user:
             return self.deny(path)