overhaul settings: split into routed sub-tabs, add server logs, changelog, reusable setting components

- Rename Server tab to Settings with horizontal sub-tab navigation (General, Generation, GPU, Logs, Changelog)
- All sub-tabs are proper routes under /settings/* with /server redirect for backwards compat
- General: connection settings, link cards (docs + discord), API reference card, app updates
- Generation: auto-chunking, crossfade, normalize, autoplay as SettingRow components
- GPU: info card with platform-aware icons (Apple logo for MPS), CUDA management, explainer text
- Logs: real-time server log viewer piped from Tauri sidecar via event system (Tauri-only)
- Changelog: parsed from CHANGELOG.md at build time via Vite virtual module plugin
- New reusable SettingRow/SettingSection components for consistent settings layout
- New Toggle (switch) UI component replacing checkboxes in settings
- Toast viewport now offsets when audio player is open
- Sidebar stays active on settings sub-routes (fuzzy matching)

app/plugins/changelog.ts

@@ -0,0 +1,23 @@
+import { readFileSync } from 'node:fs';
+import path from 'node:path';
+import type { Plugin } from 'vite';
+
+/** Vite plugin that exposes CHANGELOG.md as `virtual:changelog`. */
+export function changelogPlugin(repoRoot: string): Plugin {
+  const virtualId = 'virtual:changelog';
+  const resolvedId = '\0' + virtualId;
+  const changelogPath = path.resolve(repoRoot, 'CHANGELOG.md');
+
+  return {
+    name: 'changelog',
+    resolveId(id) {
+      if (id === virtualId) return resolvedId;
+    },
+    load(id) {
+      if (id === resolvedId) {
+        const raw = readFileSync(changelogPath, 'utf-8');
+        return `export default ${JSON.stringify(raw)};`;
+      }
+    },
+  };
+}