feat(audio-player): Resume Rewind select in the settings popover

The player window could only change Skip and Speed; resume rewind
lived exclusively on the profile page. The user-facing settings now
match Speed's precedent — changeable from the player, saved to the
account, applied immediately.

The select mirrors the default-speed row (CSP-safe @change bound to
one Alpine method; templ emits the option list from the shared
ResumeRewindOptions allow-list and the :selected expression against
the live resumeRewind field). Applying updates the running player's
value first — the next open/unpause uses it with no reload — then
PUTs audio_resume_rewind_seconds to the profile endpoint as the
string wire shape the server binds. normalizeResumeRewind gates the
select's value through 0/5/10 before both steps.

templates/types.go

@@ -1,6 +1,7 @@
 package templates
 
 import (
+	"fmt"
 	"time"
 
 	"github.com/a-h/templ"
@@ -35,6 +36,18 @@ type User struct {
 // server-side mirror of the web player's SPEEDS list (plan §5/§8).
 var SpeedOptions = []float64{0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.5, 3}
 
+// ResumeRewindOptions mirrors the server's strict allow-list for
+// audio_resume_rewind_seconds (0 = exact resume). Shared by the
+// profile form and the audio player's settings popover.
+var ResumeRewindOptions = []int{0, 5, 10}
+
+func ResumeRewindLabel(seconds int) string {
+	if seconds == 0 {
+		return "Off"
+	}
+	return fmt.Sprintf("%d s before", seconds)
+}
+
 type PageData struct {
 	User        User
 	CurrentPage string