fix(deps): revert TS6/ESLint10/webpack-cli7 majors and gate future majors (#43)

## Summary
Three Renovate major bumps merged silently because `nx affected` doesn't see deps-only PRs as affecting any project — CI passed trivially, the breakage only surfaced when `nx run-many` was run locally:

- **TypeScript 5→6** (#33) — `tsconfig.lib.json` fails with `TS5101: Option 'baseUrl' is deprecated`. Revert to 5.9.x.
- **ESLint 9→10** (#36) — `@nx/eslint@22.7.1` not compatible: project graph fails with "Unable to find eslint". Revert eslint, `@eslint/js`, `jsonc-eslint-parser`, `eslint-plugin-playwright` to ESLint-9-compatible versions.
- **webpack-cli 5→7** (#34) — webpack-cli 7 removed the `--node-env=production` flag Nx generates. Revert to 5.x.

Bonus side-fix: the `ajv@<8.18.0` override added in #42 was over-broad and was forcing ESLint's bundled ajv to v8 (incompatible with ESLint 9's option contract). Narrow the override to `@angular-devkit/core>ajv@<8.18.0` so only the targeted nestjs-prisma chain is bumped.

## Prevention — gate majors behind the dependency dashboard

Add a Renovate `packageRule` with `dependencyDashboardApproval: true` for `matchUpdateTypes: ["major"]`. Renovate stops auto-creating PRs for majors; they appear as checkboxes in the dashboard issue, and only get a PR after a human ticks the box (presumably after reading the changelog and confirming Nx-plugin / Angular / NestJS readiness).

This is the surgical fix for the gap. The deeper fix (making `nx affected` correctly mark all projects as affected on package.json changes) is a separate investigation worth doing later — but the dashboard gate prevents the same trap regardless.

## Verification
Locally on this branch:
- `pnpm exec nx run-many -t lint test build --parallel=2` → ✓ 8 projects pass.
- `pnpm audit --audit-level=moderate` → 0 vulnerabilities.

## Test plan
- [ ] `check` job goes green on this PR (would have caught the regressions if `nx affected` were broader).
- [ ] After merge, the next Renovate run does not create new PRs for any major (TS, eslint, webpack-cli, etc.).
- [ ] Any pending major in the dashboard issue still appears, but only as a checkbox awaiting approval.

## Out of scope (follow-up)
Investigate why `nx affected` misses package.json-only changes. Likely a missing entry in `nx.json` `namedInputs` (`default`) or `targetDefaults`. Worth its own focused PR; the dashboard gate is the conservative fix in the meantime.

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Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #43

docs/development.md

@@ -246,6 +246,7 @@ Repo → Actions → "Renovate" workflow → Run workflow. Useful when you've ju
 
 - Renovate PRs run a leaner CI pipeline than human PRs — `check`, `scan`, `a11y` only. The `perf` and `commits` gates are skipped (per [ADR-0017](decisions/0017-performance-budgets-lighthouse-ci.md) — Lighthouse signal on a dep bump is essentially zero, commitlint on bot-generated messages is tautological). The full `perf` gate still runs on `push` to `main` post-merge, so regressions are caught seconds after merge rather than before.
 - Don't merge until the remaining gates are green.
+- **Major bumps are gated behind the dependency dashboard.** Renovate does not auto-create PRs for major updates; instead, they appear in the "Renovate Dependency Dashboard" issue with a checkbox. Tick the box only after reading the upstream changelog and confirming the rest of our toolchain (Nx plugins, Angular CLI, NestJS, etc.) supports the new major. This guard exists because `nx affected` sees a deps-only change as not affecting any project — so a major that breaks the build can pass CI silently and only surface days later. Past offenders we caught the hard way: TypeScript 5→6 (deprecated `baseUrl`), ESLint 9→10 (Nx eslint plugin not yet compatible), webpack-cli 5→7 (removed `--node-env` flag).
 - The "Renovate Dependency Dashboard" issue (auto-created on first run) lists every pending update grouped by status. Use it to triage which PRs to expedite.
 - For a major bump that introduces breaking changes, **don't reflexively merge**: read the changelog, then either accept the work or close the PR with a "rejected" label. Renovate respects that label and won't keep re-opening the same major.
 - **Adding or removing** a dependency belongs in a feature PR, not in Renovate's scope. Renovate only updates _versions_ of existing deps.