chore: initial monorepo scaffold

Setup pnpm workspaces with apps/{web,api} placeholders and shared
packages: tsconfig, eslint-config, shared, ui, db. Includes Prettier,
ESLint, Husky pre-commit, lint-staged, EditorConfig, VSCode settings.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,41 @@
+# Dependencies
+node_modules/
+.pnpm-store/
+
+# Build output
+dist/
+build/
+.next/
+out/
+.turbo/
+
+# Test / coverage
+coverage/
+.nyc_output/
+
+# Env files (NEVER commit)
+.env
+.env.*
+!.env.example
+
+# Logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Editor
+.idea/
+*.swp
+*.swo
+
+# TypeScript
+*.tsbuildinfo
+
+# Misc
+.cache/