iPhone: step probes + full hls.js error stream to server

The play-probe now lands (iPhone: iOS 18.7 Safari, hls.js path, MSE ok),
but the /stream XHR never reaches the server on the failing attempts —
impossible under the known code path. Instrument each step
(new-hls-ok / loadsource-called / attach-ok) and log EVERY hls.js error
(fatal+non-fatal, with retry counter) so the client timeline is visible
server-side. Also fixed JSV constant drift (was stuck at 10).
events endpoint: accept hls-err, forward step/fatal/details/buffer/retry/http.

server/app.py

@@ -285,12 +285,13 @@ def api_events(evt: dict = Body(...), request: Request = None):
     # client-reported events; the diagnostics the browser can uniquely see
     # (playback failures, capability probes) happen client-side, not in the
     # request log — so the phone reports them here
-    if evt.get("type") not in ("error", "client-fail", "play-probe"):
+    if evt.get("type") not in ("error", "client-fail", "play-probe", "hls-err"):
         raise HTTPException(422, "unknown event type")
     c = db.connect()
     db.event(c, request.state.user, evt["type"],
              {k: evt[k] for k in ("ep_id", "ep", "lang", "msg", "detail",
-                                  "jsv", "branch", "hls_lib", "mse", "native_hls", "ua") if k in evt})
+                                  "jsv", "branch", "hls_lib", "mse", "native_hls", "ua",
+                                  "step", "fatal", "details", "buffer", "retry", "http") if k in evt})
     c.commit()
     c.close()
     return {"ok": True}