ci: tweak files-changed, add free-disk-space (#37819)

Reduces CI minutes consumption by narrowing the `files-changed` filters.

- DB matrix (`pgsql`/`mysql`/`mssql`/`unit`) now runs only on real
backend changes. `test-sqlite` stays gated on `actions`, so it remains
the smoke check that validates CI-infra changes (composite-action edits,
workflow edits, renovate action-pin bumps) without spinning up the full
matrix.
- Fix the `templates` filter: the SVG template linter is
`tools/lint-templates-svg.ts`, so the `tools/lint-templates-*.js` glob
matched nothing.
- Add missed paths: `tsconfig.json` and
`tools/generate-svg-vscode-extensions.json` to `frontend`,
`eslint.json.config.ts` to `json`, and
`.github/actions/docker-dryrun/**` to `docker`.

---
This PR was written with the help of Claude Opus 4.7

---------

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>

.github/workflows/files-changed.yml

@@ -69,6 +69,8 @@ jobs:
               - "*.ts"
               - "web_src/**"
               - "tools/generate-svg.ts"
+              - "tools/generate-svg-vscode-extensions.json"
+              - "tsconfig.json"
               - "assets/emoji.json"
               - "package.json"
               - "pnpm-lock.yaml"
@@ -88,13 +90,14 @@ jobs:
               - "Makefile"
 
             templates:
-              - "tools/lint-templates-*.js"
+              - "tools/lint-templates-*.ts"
               - "templates/**/*.tmpl"
               - "pyproject.toml"
               - "uv.lock"
 
             docker:
               - ".github/workflows/pull-docker-dryrun.yml"
+              - ".github/actions/docker-dryrun/**"
               - "Dockerfile"
               - "Dockerfile.rootless"
               - "docker/**"
@@ -122,6 +125,7 @@ jobs:
             json:
               - "**/*.json"
               - "**/*.json5"
+              - "eslint.json.config.ts"
 
             e2e:
               - "tests/e2e/**"