ci: drop npm/node_modules cache — runner cache server is unreachable

The act_runner's internal cache server (172.17.0.2:46367) can't be reached
from job containers: `setup-node` with `cache: npm` spends ~4m42s on
`getCacheEntry failed: connect ETIMEDOUT` every build, then reports "npm cache
is not found" — ~5 min of pure cost for zero caching. The `actions/cache`
node_modules steps added in 79258668 would hit the same dead server and hang
too, so they're removed here as well.

Removing the cache usage reclaims ~5 min/build with no loss (nothing was being
cached). The fast-gates-before-build reorder is kept. Re-enable caching once
the runner's cache server is reachable from job containers.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -30,23 +30,14 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version-file: '.node-version'
-          cache: npm
-
-      # Cache the installed tree keyed on the lockfile + Node version. On a hit
-      # (lockfile unchanged) `npm ci` — extraction + the postinstall folds patch —
-      # is skipped entirely and node_modules is just restored (the patch is baked
-      # into the cached tree). setup-node's `cache: npm` still warms the download
-      # cache for the miss path. Save runs only on a miss AND only if install
-      # succeeded (`success()`), so a failed `npm ci` can never poison the cache.
-      - name: Restore node_modules
-        id: node-modules
-        uses: actions/cache/restore@v4
-        with:
-          path: node_modules
-          key: node-modules-${{ runner.os }}-${{ hashFiles('package-lock.json', '.node-version') }}
 
+      # No npm / node_modules cache: the act_runner's internal cache server is
+      # unreachable from job containers (`getCacheEntry failed: connect ETIMEDOUT
+      # 172.17.0.2`), so every cache restore hangs ~5 min and then fails — pure
+      # cost, zero benefit. `cache: npm` was removed from Setup Node above for the
+      # same reason. Re-enable both (setup-node `cache: npm` + an actions/cache
+      # node_modules step) once the runner's cache server is reachable from jobs.
       - name: Install dependencies
-        if: steps.node-modules.outputs.cache-hit != 'true'
         # Harden against transient registry network failures (ECONNRESET etc.):
         # raise npm's built-in fetch retries/timeouts and retry `npm ci` up to
         # 3 times with backoff before failing the build.
@@ -66,13 +57,6 @@ jobs:
             sleep $((attempt * 15))
           done
 
-      - name: Save node_modules
-        if: steps.node-modules.outputs.cache-hit != 'true' && success()
-        uses: actions/cache/save@v4
-        with:
-          path: node_modules
-          key: node-modules-${{ runner.os }}-${{ hashFiles('package-lock.json', '.node-version') }}
-
       # ── Quality gates run BEFORE the slow build so a format/lint/type/test
       # error fails in seconds instead of after the ~minutes-long build. All are
       # hard gates — any failure fails the job and blocks the deploy. The tree is