remove(seekbar): drop realtime_waveform style

Downloaded and fully decoded the entire audio file on every track
change — too CPU/bandwidth intensive to keep. Removes SeekbarStyle
variant, Rust command, waveform_decode function, all frontend canvas
code, seekbarRealtime_waveform i18n keys across all 8 locales, and
unused urlencoding dependency from Cargo.toml.

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

src-tauri/src/audio.rs

@@ -3109,6 +3109,7 @@ pub fn audio_set_gapless(enabled: bool, state: State<'_, AudioEngine>) {
 //      Linux: case 2 is disabled — ALSA/cpal often omit the active sink from
 //      enumeration while streaming, which caused false resets to system default.
 
+
 pub fn start_device_watcher(engine: &AudioEngine, app: tauri::AppHandle) {
     let reopen_tx       = engine.stream_reopen_tx.clone();
     let stream_handle   = engine.stream_handle.clone();

src/components/WaveformSeek.tsx

@@ -1,7 +1,6 @@
 import React, { useEffect, useRef, useState } from 'react';
 import { usePlayerStore } from '../store/playerStore';
 import { useAuthStore, type SeekbarStyle } from '../store/authStore';
-
 function fmt(s: number): string {
   if (!s || isNaN(s)) return '0:00';
   return `${Math.floor(s / 60)}:${Math.floor(s % 60).toString().padStart(2, '0')}`;
@@ -733,7 +732,10 @@ export function SeekbarPreview({
   useEffect(() => {
     const canvas = canvasRef.current;
     if (!canvas) return;
-    const heights   = style === 'waveform' ? makeHeights('seekbar-preview-demo') : null;
+    let heights: Float32Array | null = null;
+    if (style === 'waveform') {
+      heights = makeHeights('seekbar-preview-demo');
+    }
     const animState = makeAnimState();
     let t = 0;
     const tick = () => {
@@ -818,7 +820,11 @@ export default function WaveformSeek({ trackId }: Props) {
   styleRef.current = seekbarStyle;
 
   useEffect(() => {
-    heightsRef.current = trackId ? makeHeights(trackId) : null;
+    if (!trackId) {
+      heightsRef.current = null;
+      return;
+    }
+    heightsRef.current = makeHeights(trackId);
   }, [trackId]);
 
   // Imperative subscription — no React re-renders from progress changes.