feat: release workflow with automated version bump and publish

[jaseemjaskp]

Summary

• Replaces the existing release-triggered publish workflow with a workflow_dispatch-based workflow that automates the full release process
• Supports patch, minor, and major version bumps via manual trigger input
• Automatically bumps version in src/unstract/api_deployments/__init__.py, commits, tags, creates a GitHub release, runs linting & tests, builds, and publishes to PyPI
• Adds optional pre-release flag and release notes inputs

Changes

• Trigger: on: release → on: workflow_dispatch with version bump type, pre-release, and release notes inputs
• GitHub App Token: Uses actions/create-github-app-token@v2 to push version bump commits and tags to main
• Version bump: Parses current version from __init__.py, calculates new semver, updates file, commits with [skip ci]
• Release creation: Creates git tag and GitHub release with auto-generated or custom release notes
• Quality gates: Runs ruff check for linting and pytest for tests before publishing
• Publish: Uses uv build + uv publish with Trusted Publishers

Prerequisites

The following must be configured in the repository settings:

• Repository variable: PUSH_TO_MAIN_APP_ID (GitHub App ID)
• Repository secret: PUSH_TO_MAIN_APP_PRIVATE_KEY (GitHub App private key)
• PyPI Trusted Publisher configured for this repository/workflow

Test plan

• Verify the workflow YAML is valid (syntax check)
• Confirm PUSH_TO_MAIN_APP_ID and PUSH_TO_MAIN_APP_PRIVATE_KEY are configured
• Test a dry run with patch version bump
• Verify version bump commit, tag, and GitHub release are created correctly
• Verify PyPI publish succeeds with Trusted Publishers