ci: quote the two job names - the file could not parse

The gate file has never parsed: the two job names were plain scalars
containing ': ' (YAML 1.2 plain-scalar rule - a colon followed by a space
ends the scalar and starts a mapping, so the file fails to load). Gitea
cannot build a run from a file it cannot parse, and the tell is a
dispatch POST answered HTTP 500 with an empty body.

Measured at this seat, own PAT, own repo: dispatch on main -> HTTP 500,
dispatch on this branch -> HTTP 500, 0 run records, 0 queued jobs.
Quoting the two names is the whole change; gates, labels, toolchain and
the trigger shape (workflow_dispatch: {} -> workflow_dispatch:) are
unchanged. Evidence and the follow-up dispatch live on researchx#24.

.gitea/workflows/ci.yml

@@ -50,7 +50,7 @@ on:
 
 jobs:
   backend:
-    name: backend (uv, Python 3.12: ruff/mypy/pytest)
+    name: "backend (uv, Python 3.12: ruff/mypy/pytest)"
     runs-on: ubuntu-latest
     timeout-minutes: 20
     steps:
@@ -88,7 +88,7 @@ jobs:
         run: uv run pytest
 
   frontend:
-    name: frontend (Next.js on pnpm: typecheck/lint/test/build)
+    name: "frontend (Next.js on pnpm: typecheck/lint/test/build)"
     runs-on: ubuntu-latest
     timeout-minutes: 25
     steps: