fix(ci): give Renovate a git identity and a github.com token (#13)

## Summary
First successful Renovate run (after the docker-image fix in #12) extracted 116 deps cleanly but every branch update failed with `fatal: empty ident name not allowed`, then the whole repo aborted on `Lock file error - aborting`. Two root causes:

- **No git identity** — the bot user had an email but no **Full Name** on its Gitea profile, so Renovate produced incomplete git authorship.
- **No github.com auth** — Renovate could not look up versions of GitHub-hosted Actions (`actions/checkout`, etc.) or `containerbase/node-prebuild` (the Node binary it dynamically fetches for lockfile maintenance) — anonymous rate limit (60 req/h) hit.

Fixes:

1. **`renovate.json`** — pin `gitAuthor` explicitly. The Full Name was also set on the bot's Gitea profile for UI consistency, but the override in config means we don't depend on out-of-band UI state.
2. **`.gitea/workflows/renovate.yml`** — pass `RENOVATE_GITHUB_COM_TOKEN` from the new `GITHUBCOM_TOKEN` repo secret (no underscore between GITHUB and COM — Gitea reserves the `GITHUB_*` namespace).
3. **`docs/development.md`** — onboarding procedure now covers both tokens + the Full Name step.

## Manual setup required after merge
Already done in this iteration:
- Bot's Full Name set in Gitea ("APF Portal Bot").
- `GITHUBCOM_TOKEN` repo secret created with a zero-scope github.com PAT.

(If the PAT was leaked during setup, regenerate before merging — the workflow only references the secret name, not the value.)

## Test plan
- [ ] After merge, trigger Renovate manually (Actions → Renovate → Run workflow).
- [ ] No `empty ident name` warning in the logs.
- [ ] No `Lock file error - aborting`; repo finishes with `INFO: Repository finished … "cloned": true`.
- [ ] Renovate creates the dependency dashboard issue + the first batch of grouped PRs (Angular, Nx, NestJS, Prisma, …) signed by `apf-portal-bot`.

---------

Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #13

renovate.json

@@ -1,6 +1,7 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": ["config:recommended"],
+  "gitAuthor": "APF Portal Bot <jgautier.webdev+apf-portal-bot@gmail.com>",
   "dependencyDashboard": true,
   "dependencyDashboardTitle": "Renovate Dependency Dashboard",
   "labels": ["dependencies"],