ci(deploy): switch from Cloudflare Pages to GitHub Pages

Migrate build and deployment pipeline from Cloudflare Pages to GitHub Pages.
Adds production-ready deploy workflow in deploy-github-pages.yml with proper
artifact handling. Removes Cloudflare-specific tooling: wrangler config, _headers,
_redirects, and CSP hash injection scripts (no longer needed with GitHub Pages
static hosting). Updates package.json build scripts and all project documentation
to reflect new deployment target and simplified architecture.

web/package.json

@@ -6,13 +6,12 @@
   "scripts": {
     "dev": "vite dev",
     "dev:codeserver": "VITE_DEV_PROFILE=codeserver vite dev --host 0.0.0.0",
-    "build": "vite build && node scripts/inject-csp-hashes.mjs",
-    "build:gh": "BUILD_PROFILE=gh vite build && node scripts/inject-csp-hashes.mjs",
+    "build": "vite build",
+    "build:gh": "BUILD_PROFILE=gh vite build",
     "preview": "vite preview",
     "lint": "eslint .",
     "test": "vitest run",
-    "test:watch": "vitest",
-    "verify:build": "node scripts/verify-build-inline-scripts.mjs"
+    "test:watch": "vitest"
   },
   "optionalDependencies": {
     "lightningcss-linux-x64-gnu": "1.32.0"