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/advanced-calibration.ts

@@ -280,7 +280,7 @@ export function selectCalibrationLine(idx: number): void {
     const prev = _state.selectedLine;
     _state.selectedLine = idx;
     // Update selection in-place without rebuilding the list DOM
-    const container = document.getElementById('advcal-line-list');
+    const container = document.getElementById('advcal-line-list')!;
     const items = container.querySelectorAll('.advcal-line-item');
     if (prev >= 0 && prev < items.length) items[prev].classList.remove('selected');
     if (idx >= 0 && idx < items.length) items[idx].classList.add('selected');
@@ -361,14 +361,14 @@ function _buildMonitorLayout(psList: any[], cssId: string | null): void {
     // Load saved positions from localStorage
     const savedKey = `advcal_positions_${cssId}`;
     let saved = {};
-    try { saved = JSON.parse(localStorage.getItem(savedKey)) || {}; } catch { /* ignore */ }
+    try { saved = JSON.parse(localStorage.getItem(savedKey) ?? '{}') || {}; } catch { /* ignore */ }
 
     const canvas = document.getElementById('advcal-canvas') as HTMLCanvasElement;
     const canvasW = canvas.width;
     const canvasH = canvas.height;
 
     // Default layout: arrange monitors in a row
-    const monitors = [];
+    const monitors: any[] = [];
     const padding = 20;
     const maxMonW = (canvasW - padding * 2) / Math.max(psList.length, 1) - 10;
     const monH = canvasH * 0.6;
@@ -423,7 +423,7 @@ function _placeNewMonitor(): void {
 
 function _updateTotalLeds(): void {
     const used = _state.lines.reduce((s, l) => s + l.led_count, 0);
-    const el = document.getElementById('advcal-total-leds');
+    const el = document.getElementById('advcal-total-leds')!;
     if (_state.totalLedCount > 0) {
         el.textContent = `${used}/${_state.totalLedCount}`;
         el.style.color = used > _state.totalLedCount ? 'var(--danger-color, #ff5555)' : '';
@@ -436,7 +436,7 @@ function _updateTotalLeds(): void {
 /* ── Line list rendering ────────────────────────────────────── */
 
 function _renderLineList(): void {
-    const container = document.getElementById('advcal-line-list');
+    const container = document.getElementById('advcal-line-list')!;
     container.innerHTML = '';
 
     _state.lines.forEach((line, i) => {
@@ -470,7 +470,7 @@ function _renderLineList(): void {
 }
 
 function _showLineProps(): void {
-    const propsEl = document.getElementById('advcal-line-props');
+    const propsEl = document.getElementById('advcal-line-props')!;
     const idx = _state.selectedLine;
     if (idx < 0 || idx >= _state.lines.length) {
         propsEl.style.display = 'none';
@@ -553,7 +553,7 @@ function _fitView(): void {
 function _renderCanvas(): void {
     const canvas = document.getElementById('advcal-canvas') as HTMLCanvasElement | null;
     if (!canvas) return;
-    const ctx = canvas.getContext('2d');
+    const ctx = canvas.getContext('2d')!;
     const W = canvas.width;
     const H = canvas.height;
 
@@ -679,7 +679,7 @@ function _drawLineTicks(ctx: CanvasRenderingContext2D, line: CalibrationLine, x1
             return (line.reverse ? (1 - f) : f) * edgeLen;
         };
 
-        const placed = [];
+        const placed: number[] = [];
 
         // Place intermediate labels at nice steps
         for (let i = 0; i < count; i++) {