Add per-channel hybrid audio spread spectrum and env feature toggles

Spread spectrum v2: independent per-channel embedding with round-robin
bit distribution, preserving spatial stereo/surround mix. Adaptive chip
tiers (256/512/1024) trade capacity for lossy codec robustness. LFE
channel skipped for 5.1+ layouts. v2 header (20B) with backward-
compatible v0 decode fallback.

Environment toggles (STEGASOO_AUDIO, STEGASOO_VIDEO) gate audio/video
features for minimal builds (e.g. Raspberry Pi image-only). Values:
auto (default, detect deps), 1/true (force on), 0/false (force off).

Web UI fixes: accordion defaults to step 1 on load, chevron arrow
styling, required attribute toggling for audio carrier type switch,
"Images & Mode" renamed to "Reference, Carrier, Mode".

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

aur-cli/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Aaron D. Lee <your-email@example.com>
 pkgname=stegasoo-cli-git
-pkgver=4.2.1
+pkgver=4.3.0
 pkgrel=1
 pkgdesc="Secure steganography CLI with hybrid photo + passphrase + PIN authentication"
 arch=('x86_64')
@@ -29,7 +29,7 @@ sha256sums=('SKIP')
 pkgver() {
     cd "$pkgname"
     git describe --long --tags 2>/dev/null | sed 's/^v//;s/\([^-]*-g\)/r\1/;s/-/./g' || \
-    printf "%s.r%s.g%s" "4.2.1" "$(git rev-list --count HEAD)" "$(git rev-parse --short HEAD)"
+    printf "%s.r%s.g%s" "4.3.0" "$(git rev-list --count HEAD)" "$(git rev-parse --short HEAD)"
 }
 
 build() {