chore(release): v1.40.0

Major release consolidating several months of work into a single coherent
version. The 1.34.x patch series accumulated many small features; 1.40.0
packages them up and signals the infrastructure milestone (macOS signing
+ notarization + auto-updater) clearly.

Highlights (see CHANGELOG for the full rundown):
- macOS builds are signed with a Developer ID certificate and notarized
  by Apple — no more Gatekeeper "unidentified developer" dialog
- In-app auto-update on macOS via the Tauri Updater plugin; polished
  modal with trust badges, restart countdown, and state-dependent buttons
- Linux WebKitGTK wheel scroll toggle (PR #207 by cucadmuh)
- Device Sync: user-configurable filename template replaced with a
  fixed cross-OS scheme; playlists now live in their own self-contained
  folders with sibling-referencing .m3u8; one-shot migration tool for
  existing sticks
- WCAG contrast audits for middle-earth and nucleo themes
- Contributors list in Settings → About updated (PRs #205, #206, #207)

Windows signing + Windows auto-updater are the remaining gap; 2.0.0 is
planned once both are active.

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

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Psysonic",
-  "version": "1.34.23",
+  "version": "1.40.0",
   "identifier": "dev.psysonic.player",
   "build": {
     "beforeDevCommand": "npm run dev",