cleanup: remove build artifacts, generated files, and byproducts

- Removed frontend/node_modules directory (251MB)
- Removed frontend/dist build artifacts (496KB)
- Removed Python __pycache__ directories
- Removed compiled binaries from build/bin/ (14.1MB)
- Removed build/windows/installer/tmp temporary directory (1.7MB)
- Removed coverage.out (Go test coverage report - 67KB)
- Removed frontend/package.json.md5 (generated checksum file)
- Removed endpoints/echo-model/.policy_store.db (SQLite database)

Updated .gitignore with comprehensive exclusions for:
- Go coverage and profiling artifacts (*.prof, *.pprof)
- Test artifacts (.coverage, .pytest_cache, htmlcov)
- Python cache files (__pycache__, *.pyc)
- Generated checksums (*.md5, *.sha256, *.sha1)
- Editor files (*.swp, *.swo, *~)
- OS-specific files (.DS_Store, Thumbs.db)
- IDE configuration files (.vscode, .idea)
- Build artifacts and temporary files

Reduces repo size from ~300MB to 1.4MB (excluding .git)

Author: IonesioJunior

syfthub-desktop/.gitignore

@@ -1,3 +1,51 @@
 build/bin
+build/windows/installer/tmp
 node_modules
+frontend/node_modules
 frontend/dist
+__pycache__
+*.pyc
+*.pyo
+*.pyd
+.Python
+*.so
+.DS_Store
+Thumbs.db
+.vscode/settings.json
+.idea/
+*.log
+.env
+.env.local
+
+# Go coverage and profiling
+coverage.out
+*.prof
+*.pprof
+*.test
+
+# Test and build artifacts
+.coverage
+.pytest_cache/
+.tox/
+htmlcov/
+*.egg-info/
+dist/
+build/
+
+# Editor and IDE files
+*.swp
+*.swo
+*~
+.DS_Store
+.vscode/
+.idea/
+*.iml
+
+# Temporary files
+*.tmp
+*.temp
+
+# Generated checksums and build metadata
+*.md5
+*.sha256
+*.sha1