Add a web player lyrics panel with active-line highlighting and click-to-seek

New GET /player/lyrics/{id} (auth-required) returns the best available
stored structuredLyrics entry for a song — preferring a synced one —
as plain JSON lines with a start time only where the source actually
has one.

The player bar gains a lyrics toggle; the panel fetches lyrics on
every song change, renders each line, and — only for lines that
actually carry a startMs — makes them clickable (seeks + plays) and
highlights the currently active line as playback progresses. Plain
(unsynced) lyrics render as static text with no fabricated timing or
highlighting.

Note: verified via Go template parsing/rendering and the new handler
tests, plus a JS syntax check; not manually exercised in a browser in
this session.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014r98AtcBbevpscWLsfwVvv

internal/web/lyrics_handler.go

@@ -0,0 +1,50 @@
+package web
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"git.noroutes.net/NoRoutes/vibetunes/internal/database"
+)
+
+type lyricsLineJSON struct {
+	Text    string `json:"text"`
+	StartMs *int   `json:"startMs,omitempty"`
+}
+
+type lyricsResponseJSON struct {
+	Synced bool             `json:"synced"`
+	Lines  []lyricsLineJSON `json:"lines"`
+}
+
+// handleLyrics serves the web player's lyrics panel: the best available
+// stored structuredLyrics entry for a song, as line text plus a start
+// time when the source actually has one. Prefers a synced entry over
+// an unsynced one so the panel can highlight/click-to-seek whenever
+// that data exists, but never fabricates timing for an unsynced entry.
+func (h *Web) handleLyrics(w http.ResponseWriter, r *http.Request) {
+	songID := r.PathValue("id")
+	entries, err := database.GetSongStructuredLyrics(h.DB, songID)
+	if err != nil {
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+
+	var best *database.StructuredLyricsRow
+	for i := range entries {
+		if best == nil || (entries[i].Synced && !best.Synced) {
+			best = &entries[i]
+		}
+	}
+
+	out := lyricsResponseJSON{Lines: []lyricsLineJSON{}}
+	if best != nil {
+		out.Synced = best.Synced
+		for _, l := range best.Lines {
+			out.Lines = append(out.Lines, lyricsLineJSON{Text: l.Text, StartMs: l.StartMs})
+		}
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	_ = json.NewEncoder(w).Encode(out)
+}