feat: listen analytics — track who heard what and when

Add listen_events table to record opens, plays and listen duration per
share link. Public POST/PATCH endpoints for fire-and-forget tracking
from the listen page; authenticated GET analytics endpoint aggregates
per version. Listen page gains optional name prompt after first play
and sendBeacon on unload. Track page gains Analytics tab with stats
grid and per-listener event list.

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

packages/shared/src/validation/push.ts

@@ -8,3 +8,10 @@ export const subscribePushSchema = z.object({
   }),
   userAgent: z.string().optional(),
 });
+
+export const updateListenEventSchema = z.object({
+  listenerName: z.string().max(255).optional(),
+  firstPlay: z.boolean().optional(),
+  listenSeconds: z.number().int().min(0).optional(),
+  completed: z.boolean().optional(),
+});