chore: overhaul renovate preset config, docs, and tooling

- Switch schema to renovate-global-schema.json
- Remove redundant/deprecated settings and presets
- Add Makefile custom manager for tool version tracking
- Add package groups: illuminate, semantic-release, stylelint,
  tailwind, vite, vue, development tools
- Add check-jsonschema pre-commit hook
- Add .gitignore and CLAUDE.md
- Rewrite README with comprehensive preset documentation

CLAUDE.md

@@ -0,0 +1,40 @@
+# CLAUDE.md
+
+## Project overview
+
+Shared [Renovate](https://github.com/renovatebot/renovate) preset configuration for repositories managed by ivuorinen. Other repos consume this preset via `"extends": ["github>ivuorinen/renovate-config"]` in their Renovate config.
+
+## Repository structure
+
+```
+default.json                 # The shared Renovate preset (this is the main artifact)
+.github/renovate.json        # This repo's own Renovate config (self-referencing)
+.pre-commit-config.yaml      # Pre-commit hooks including config validation
+.editorconfig                # Editor conventions
+LICENSE                      # MIT
+README.md                    # Usage instructions
+```
+
+## Validation
+
+Run the pre-commit hook to validate `default.json`:
+
+```sh
+pre-commit run --all-files
+```
+
+This runs two validators against `default.json`: `renovate-config-validator --strict` (Renovate's own validator) and `check-renovate` (JSON Schema validation via [check-jsonschema](https://github.com/python-jsonschema/check-jsonschema)). The hooks also enforce JSON formatting (`pretty-format-json --autofix --no-ensure-ascii`), trailing whitespace removal, and other checks.
+
+## How default.json works
+
+- Extends `config:recommended` and several Renovate built-in presets
+- Defines `packageRules` for automerge (minor/patch), labeling by update type and datasource, and grouping (devDependencies, eslint, phpstan)
+- Includes a `customManagers` regex manager for Dockerfile ENV/FROM version extraction
+- Configures semantic commits (`chore(deps):` scope), squash automerge strategy, and non-office-hours schedule (Europe/Helsinki)
+- Sets `postUpdateOptions` for lock file deduplication across bundler, composer, go, npm, pnpm, and yarn
+
+## Conventions
+
+- 2-space indentation, UTF-8, LF line endings, final newline (per `.editorconfig`)
+- JSON keys in `default.json` are sorted alphabetically
+- No build system, no tests, no application code