Add Nebula Browser app, UI and assets

Add initial Nebula Browser project skeleton: CMakeLists to configure and link CEF (including post-build steps to copy runtime and UI files), a Windows CEF-based entry (app/main.cpp) that initializes CEF and loads the bundled UI, and a full ui/ and assets/ tree (HTML, CSS, JS, fonts, icons, and branding images). Update .gitignore to ignore build/out, thirdparty/cef, IDE and common OS artifacts.

.gitignore

@@ -1,116 +1,20 @@
-# Logs
-logs
-*.log
-npm-debug.log*
-yarn-debug.log*
-yarn-error.log*
-lerna-debug.log*
+# Build output
+/build/
+/out/
 
-# Runtime data
-pids
-*.pid
-*.seed
-*.pid.lock
+# CEF binaries
+/thirdparty/cef/
 
-# Directory for instrumented libs generated by jscoverage/JSCover
-lib-cov
+# Visual Studio
+.vs/
+*.vcxproj.user
 
-# Coverage directory used by tools like istanbul
-coverage
-*.lcov
+# CMake
+CMakeCache.txt
+CMakeFiles/
 
-# nyc test coverage
-.nyc_output
-
-# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-temporary-files)
-.grunt
-
-# Bower dependency directory (https://bower.io/)
-bower_components
-
-# node-waf configuration
-.lock-wscript
-
-# Compiled binary addons (http://nodejs.org/api/addons.html)
-build/Release
-
-# Dependency directories
-node_modules/
-jspm_packages/
-
-# TypeScript v1 declaration files
-typings/
-
-# Optional npm cache directory
-.npm
-
-# Optional eslint cache
-.eslintcache
-
-# Optional REPL history
-.node_repl_history
-
-# Output of 'npm pack'
-*.tgz
-
-# Yarn Integrity file
-.yarn-integrity
-
-# dotenv environment variables file
-.env
-.env.test
-
-# parcel-bundler cache (https://parceljs.org/)
-.cache
-
-# Mac files
+# macOS
 .DS_Store
-.AppleDouble
-.LSOverride
-
-# Electron build output
-/dist
-/out
-/release
-/build
-*.nupkg
-*.AppImage
-*.dmg
-*.exe
-*.pkg
-
-# IDE config files
-.vscode/
-.idea/
-
-site-history.json
-bookmarks.json
-bookmarks.backup.json
-search-history.json
-
-# Portable user data folder
-user-data/
-
-# AppImage / SteamOS
-squashfs-root/
-*.AppImage
-
-# Electron build output
-dist/
-build/
-out/
-release/
-
-# Native binaries
-nebula
-nebula.exe
-
-# Node/Electron
-node_modules/
 
 # Logs
-*.log
-
-# Build artifacts
-nebula-appdir/
-*.asar
+*.log