ci(gitea): cache DENO_DIR keyed on deno.lock

setup-deno's built-in cache stores fetched JSR/npm modules and
compiled dependencies across runs. Keying on the lockfile hash
invalidates the cache only when dependencies change.

.gitea/workflows/ci.yml

@@ -14,6 +14,8 @@ jobs:
       - uses: denoland/setup-deno@v2
         with:
           deno-version: v2.x
+          cache: true
+          cache-hash: ${{ hashFiles('deno.lock') }}
 
       - name: Format check
         run: deno fmt --check