Bump version to 4.0.1 with Web UI improvements

- Update version to 4.0.1 across constants.py, __init__.py, pyproject.toml, README
- Refactor channel key UI from radio buttons to select dropdown
- Add LED indicator and key capsule CSS styles
- Reorganize encode/decode forms: RSA key section moved up, PIN + Channel in row
- Streamline channel key JavaScript for dropdown-based selection

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontends/web/static/style.css

@@ -1323,3 +1323,58 @@ footer {
     font-weight: 600;
     font-size: 0.5rem;
 }
+
+/* ----------------------------------------------------------------------------
+   LED Indicator
+   ---------------------------------------------------------------------------- */
+.led-indicator {
+    display: inline-block;
+    width: 6px;
+    height: 6px;
+    border-radius: 50%;
+    vertical-align: middle;
+}
+
+.led-yellow {
+    background: #fbbf24;
+    box-shadow: 0 0 3px #fbbf24, 0 0 6px rgba(251, 191, 36, 0.4);
+}
+
+.led-green {
+    background: #22c55e;
+    box-shadow: 0 0 3px #22c55e, 0 0 6px rgba(34, 197, 94, 0.4);
+}
+
+.led-red {
+    background: #ef4444;
+    box-shadow: 0 0 3px #ef4444, 0 0 6px rgba(239, 68, 68, 0.4);
+}
+
+/* LED Badge backgrounds */
+.led-badge-yellow {
+    background: rgba(251, 191, 36, 0.2);
+    border: 1px solid rgba(251, 191, 36, 0.4);
+    color: #fbbf24;
+}
+
+.led-badge-green {
+    background: rgba(34, 197, 94, 0.2);
+    border: 1px solid rgba(34, 197, 94, 0.4);
+    color: #22c55e;
+}
+
+.led-badge-red {
+    background: rgba(239, 68, 68, 0.2);
+    border: 1px solid rgba(239, 68, 68, 0.4);
+    color: #ef4444;
+}
+
+/* Key capsule container */
+.key-capsule {
+    display: inline-flex;
+    align-items: center;
+    border: 1px dashed rgba(255, 255, 255, 0.3);
+    border-radius: 0.375rem;
+    padding: 0.35rem 0.75rem;
+    background: rgba(0, 0, 0, 0.1);
+}