refactor: use pre-commit in GitHub

[moritzzimmer]

This PR refactors static analysis and release tooling to consolidate Terraform formatting, validation, linting, and security scanning under pre-commit, replacing bespoke Makefile targets and simplifying the GitHub Actions workflow.

It adds a dedicated Trivy config file and updates documentation/examples and PR title validation.

• Introduces trivy.yaml and routes Trivy settings through pre-commit
• Replaces individual fmt/validate/tflint/trivy GitHub jobs with matrix-driven pre-commit runs for automatically detected min/max Terraform based on versions.tf using same pre-commit hooks as locally
• desired version bump now needs to be declared explicitly

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Makefile:1

• BUMP is now intended to be a required explicit input (enforced by check-bump), but NEXT_VERSION is still computed here with a silent fallback to a patch bump when BUMP is unset or invalid. This undermines the explicit requirement and can produce an unintended version if a user runs unrelated targets that expand NEXT_VERSION. Move validation before this logic (e.g. using an ifndef + $(error ...)) or defer NEXT_VERSION calculation into the bump-version recipe after check-bump passes.

DESCRIBE           := $(shell git fetch --all > /dev/null && git describe --match "v*" --always --tags)

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