feat: add storage module with S3 support and development tooling

Create shared storage module for AWS S3 operations with comprehensive
development infrastructure:

Core Features:
- S3 interface with two upload patterns (manager and direct)
- Presigned URL generation with 15-minute expiration
- Support for multipart uploads and direct PutObject
- Comprehensive test coverage (8 tests, 70.4% coverage)
- Generic implementation without project-specific dependencies

Development Tooling:
- .editorconfig for consistent editor settings
- .pre-commit-config.yaml with Go linters and formatters
- .golangci.yml for golangci-lint configuration
- commitlint.config.js for conventional commit validation
- cliff.toml for automated changelog generation (v0.0.1)
- renovate.json for automated dependency updates
- .gitlab-ci.yml for CI/CD pipeline

CI/CD Pipeline:
- Automated testing with race detection
- Coverage tracking and Codecov integration
- Vulnerability scanning with govulncheck
- Pre-commit validation gates
- Release automation

Module exports:
- New(bucket) - Upload manager pattern for large files
- NewS3(cfg, bucket) - Direct upload pattern
- Store(path, content, contentType) - Upload and get presigned URL

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.editorconfig

@@ -0,0 +1,11 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+trim_trailing_whitespace = true
+
+[*.go]
+indent_style = tab
+indent_size = 2