```

chore: enhance .gitignore and remove obsolete documentation files

- Reorganize .gitignore with categorized sections for better maintainability
- Add comprehensive ignore patterns for Python, Node.js, databases, logs, and build artifacts
- Add project-specific ignore rules for coordinator, explorer, and deployment files
- Remove outdated documentation: BITCOIN-WALLET-SETUP.md, LOCAL_ASSETS_SUMMARY.md, README-CONTAINER-DEPLOYMENT.md, README-DOMAIN-DEPLOYMENT.md
```

.gitignore

@@ -1,6 +1,8 @@
 # AITBC Monorepo ignore rules
 
+# ===================
 # Python
+# ===================
 __pycache__/
 *.pyc
 *.pyo
@@ -9,30 +11,134 @@ __pycache__/
 .venv/
 */.venv/
 venv/
+env/
+*.egg-info/
+*.egg
+.eggs/
+pip-wheel-metadata/
+.pytest_cache/
+.coverage
+htmlcov/
+.tox/
+.mypy_cache/
+.ruff_cache/
+
+# Environment files
 *.env
 *.env.*
+.env.local
+.env.*.local
 
-# Databases & Alembic artifacts
+# ===================
+# Databases
+# ===================
 *.db
+*.sqlite
+*.sqlite3
 */data/*.db
+data/
+
+# Alembic
 alembic.ini
 migrations/versions/__pycache__/
 
-# Node / JS
+# ===================
+# Node / JavaScript
+# ===================
 node_modules/
 dist/
 build/
 .npm/
+.pnpm/
 yarn.lock
 package-lock.json
 pnpm-lock.yaml
+.next/
+.nuxt/
+.cache/
 
-# Editor
+# ===================
+# Logs & Runtime
+# ===================
+logs/
+*.log
+*.log.*
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pids/
+*.pid
+*.seed
+
+# ===================
+# Editor & IDE
+# ===================
 .idea/
 .vscode/
 *.swp
 *.swo
+*~
+.project
+.classpath
+.settings/
 
-# OS
+# ===================
+# OS Files
+# ===================
 .DS_Store
+.DS_Store?
+._*
 Thumbs.db
+ehthumbs.db
+Desktop.ini
+
+# ===================
+# Build & Compiled
+# ===================
+*.o
+*.a
+*.lib
+*.dll
+*.dylib
+target/
+out/
+
+# ===================
+# Secrets & Credentials
+# ===================
+*.pem
+*.key
+*.crt
+*.p12
+secrets/
+credentials/
+.secrets
+
+# ===================
+# Temporary Files
+# ===================
+tmp/
+temp/
+*.tmp
+*.temp
+*.bak
+*.backup
+
+# ===================
+# Project Specific
+# ===================
+# Coordinator database
+apps/coordinator-api/src/*.db
+
+# Explorer build artifacts
+apps/explorer-web/dist/
+
+# Local test data
+tests/fixtures/generated/
+
+# GPU miner local configs
+scripts/gpu/*.local.py
+
+# Deployment secrets
+scripts/deploy/*.secret.*
+infra/nginx/*.local.conf