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.

---------

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

renovate.json

@@ -16,6 +16,11 @@
     "labels": ["security", "dependencies"]
   },
   "packageRules": [
+    {
+      "matchUpdateTypes": ["major"],
+      "dependencyDashboardApproval": true,
+      "description": "Major bumps require explicit approval via the dependency dashboard (tick the entry to release the PR). Auto-creating major PRs has caused silent build regressions: TypeScript 5→6, ESLint 9→10, and webpack-cli 5→7 all passed CI through `nx affected` (which sees a deps-only change as not affecting any project) and only surfaced when run-many was attempted locally. Forcing a human in the loop on majors prevents the same trap. Patch and minor bumps still flow automatically."
+    },
     {
       "groupName": "Angular",
       "matchPackageNames": [