refactor: comprehensive code quality, security, and release readiness improvements

Security: tighten CORS defaults, add webhook rate limiting, fix XSS in
automations, guard WebSocket JSON.parse, validate ADB address input,
seal debug exception leak, URL-encode WS tokens, CSS.escape in selectors.

Code quality: add Pydantic models for brightness/power endpoints, fix
thread safety and name uniqueness in DeviceStore, immutable update
pattern, split 6 oversized files into 16 focused modules, enable
TypeScript strictNullChecks (741→102 errors), type state variables,
add dom-utils helper, migrate 3 modules from inline onclick to event
delegation, ProcessorDependencies dataclass.

Performance: async store saves, health endpoint log level, command
palette debounce, optimized entity-events comparison, fix service
worker precache list.

Testing: expand from 45 to 293 passing tests — add store tests (141),
route tests (25), core logic tests (42), E2E flow tests (33), organize
into tests/api/, tests/storage/, tests/core/, tests/e2e/.

DevOps: CI test pipeline, pre-commit config, Dockerfile multi-stage
build with non-root user and health check, docker-compose improvements,
version bump to 0.2.0.

Docs: rewrite CLAUDE.md (202→56 lines), server/CLAUDE.md (212→76),
create contexts/server-operations.md, fix .js→.ts references, fix env
var prefix in README, rewrite INSTALLATION.md, add CONTRIBUTING.md and
.env.example.

server/src/wled_controller/static/js/features/audio-sources.ts

@@ -439,7 +439,7 @@ function _sizeCanvas(canvas: HTMLCanvasElement) {
     canvas.width = rect.width * dpr;
     canvas.height = 200 * dpr;
     canvas.style.height = '200px';
-    canvas.getContext('2d').scale(dpr, dpr);
+    canvas.getContext('2d')!.scale(dpr, dpr);
 }
 
 function _renderLoop() {
@@ -449,11 +449,40 @@ function _renderLoop() {
     }
 }
 
+// ── Event delegation for audio source card actions ──
+
+const _audioSourceActions: Record<string, (id: string) => void> = {
+    'test-audio': testAudioSource,
+    'clone-audio': cloneAudioSource,
+    'edit-audio': editAudioSource,
+};
+
+export function initAudioSourceDelegation(container: HTMLElement): void {
+    container.addEventListener('click', (e: MouseEvent) => {
+        const btn = (e.target as HTMLElement).closest<HTMLElement>('[data-action]');
+        if (!btn) return;
+
+        const action = btn.dataset.action;
+        const id = btn.dataset.id;
+        if (!action || !id) return;
+
+        // Only handle audio-source actions (prefixed with audio-)
+        const handler = _audioSourceActions[action];
+        if (handler) {
+            // Verify we're inside an audio source section
+            const section = btn.closest<HTMLElement>('[data-card-section="audio-multi"], [data-card-section="audio-mono"]');
+            if (!section) return;
+            e.stopPropagation();
+            handler(id);
+        }
+    });
+}
+
 function _renderAudioSpectrum() {
     const canvas = document.getElementById('audio-test-canvas') as HTMLCanvasElement | null;
     if (!canvas) return;
 
-    const ctx = canvas.getContext('2d');
+    const ctx = canvas.getContext('2d')!;
     const dpr = window.devicePixelRatio || 1;
     const w = canvas.width / dpr;
     const h = canvas.height / dpr;