feat: cache-control overhaul so visual changes propagate immediately

Per-file content-hash versioning on every /static reference, immutable cache
headers on versioned URLs, no-cache on HTML, auto-bumped service worker cache
name with stale-while-revalidate for assets, and a controllerchange listener
that silently reloads the page when a new SW takes control.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/routes.py

@@ -1,8 +1,8 @@
 import json
 
-from flask import abort, render_template, jsonify, send_from_directory
+from flask import abort, make_response, render_template, jsonify, send_from_directory
 
-from app import app
+from app import APP_VERSION, app, static_v
 from app.config import SCOREBOARD_DATA_FILE
 from app.games import parse_games
 from app.playoff import today_meta
@@ -39,7 +39,17 @@ def manifest():
 
 @app.route("/sw.js")
 def service_worker():
-    response = send_from_directory(app.static_folder, "sw.js")
+    precache = [
+        "/",
+        static_v("styles.css"),
+        static_v("script.js"),
+        static_v("icon-192x192.png"),
+        static_v("icon-512x512.png"),
+        "/manifest.json",
+    ]
+    body = render_template("sw.js.j2", app_version=APP_VERSION, precache=precache)
+    response = make_response(body)
+    response.headers["Content-Type"] = "application/javascript; charset=utf-8"
     response.headers["Service-Worker-Allowed"] = "/"
     response.headers["Cache-Control"] = "no-cache"
     return response