Web Push: goal, kickoff and full-time alerts for a followed team

Fully progressive: without VAPID keys in the environment the API says
404, the bell never renders, and the service worker addition (a push
handler via workbox importScripts — no SW strategy change) is inert.
With keys: a bell on each team page requests permission, subscribes
(one team per device) and the server diffs fixture states on every
broadcast to push Kickoff / Goal / Full time to that team's followers.
Dead endpoints (404/410) self-clean. Round-trip verified locally with
dev VAPID keys; disabled mode verified too.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/db/db.ts

@@ -93,6 +93,13 @@ CREATE TABLE IF NOT EXISTS prediction_snapshots (
   market_json TEXT
 );
 
+CREATE TABLE IF NOT EXISTS push_subs (
+  endpoint   TEXT PRIMARY KEY,
+  json       TEXT NOT NULL,
+  team       TEXT,
+  created_at INTEGER NOT NULL
+);
+
 CREATE TABLE IF NOT EXISTS inplay_history (
   fixture_num INTEGER NOT NULL,
   minute      INTEGER NOT NULL,
@@ -147,6 +154,31 @@ export function cacheSet(key: string, value: string, ttl: number): void {
     .run(key, value, Date.now(), ttl);
 }
 
+// ---- Web Push subscriptions (goal/kickoff notifications, opt-in per team) ----
+export interface PushSub {
+  endpoint: string;
+  json: string;
+  team: string | null;
+}
+
+export function addPushSub(endpoint: string, json: string, team: string | null): void {
+  db()
+    .prepare('INSERT OR REPLACE INTO push_subs (endpoint, json, team, created_at) VALUES (?, ?, ?, ?)')
+    .run(endpoint, json, team, Date.now());
+}
+
+export function removePushSub(endpoint: string): void {
+  db().prepare('DELETE FROM push_subs WHERE endpoint = ?').run(endpoint);
+}
+
+export function pushSubsForTeams(teams: string[]): PushSub[] {
+  if (teams.length === 0) return [];
+  const marks = teams.map(() => '?').join(',');
+  return db()
+    .prepare(`SELECT endpoint, json, team FROM push_subs WHERE team IN (${marks})`)
+    .all(...teams) as unknown as PushSub[];
+}
+
 // ---- in-play win-probability history (the momentum curve on match pages) ----
 export interface InplayPoint {
   minute: number;