fix(ci): replace gitleaks-action with manual install

`gitleaks/gitleaks-action@v2` is now paywalled for organisations:
the action errors out with `🛑 missing gitleaks license. Go grab one
at gitleaks.io and store it as a GitHub Secret named
GITLEAKS_LICENSE.` Worse, it cannot reliably detect personal-vs-org
on Gitea (the GitHub API contract differs), so it defaults to
license enforcement and the scan fails. The gitleaks binary itself
remains MIT-licensed and free.

Mirror the pattern we just adopted for Trivy in #45: drop the
wrapper, install the binary directly via curl + tar from the GitHub
release, run the CLI. This:

- removes a third-party action dependency we did not need;
- pins the gitleaks version explicitly;
- harmonises with the Trivy step that lives next to it.

Apply the same change to `.gitea/workflows/security-scheduled.yml`
in the same PR — it had both broken integrations (`trivy-action
@master` plus `gitleaks-action@v2`) and was waiting silently to
fail at next Monday's cron.

Per-PR gitleaks scan uses `--no-git --source .` (working tree only)
since the scan job uses a shallow checkout; the weekly scheduled
job switches to a full clone (`fetch-depth: 0`) and runs gitleaks
in deep-history mode (default), which is the value-add of the
scheduled job over the per-PR gate.

`--redact` is added on both invocations so any matched secret is
masked in the CI log itself (no leak via the log artefact).

Also drop `cache: 'pnpm'` from `actions/setup-node` in the
scheduled workflow — we already removed it from ci.yml in #8 (the
act_runner cache server is unreachable from job containers; every
restore burns ~2 min ETIMEDOUT for zero hits). Consistency.

.gitea/workflows/security-scheduled.yml

@@ -15,24 +15,60 @@ jobs:
   full-tree-scan:
     runs-on: [self-hosted, on-prem]
     steps:
+      # fetch-depth: 0 → full history. The per-PR gitleaks scan is
+      # shallow + working-tree-only; this scheduled job is where we
+      # do the deep history scan that catches secrets ever committed
+      # (and not just what's currently checked in).
       - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
       - uses: pnpm/action-setup@v6
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: 'pnpm'
       - run: pnpm install --frozen-lockfile
       - run: pnpm audit
       # Full-tree Trivy (no skip-dirs, no severity filter — the per-PR
       # gate filters by severity for speed; this run wants the full
-      # surface for the security feed).
-      - uses: aquasecurity/trivy-action@master
-        with:
-          scan-type: fs
-          ignore-unfixed: true
-      - uses: gitleaks/gitleaks-action@v2
+      # surface for the security feed). Manual install + curl, same
+      # pattern as ci.yml — see the rationale there.
+      - name: Install Trivy
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          TRIVY_VERSION: '0.70.0'
+          GITHUB_TOKEN: ${{ secrets.GITHUBCOM_TOKEN }}
+        run: |
+          curl -sfL \
+            -H "Authorization: Bearer ${GITHUB_TOKEN}" \
+            -o /tmp/trivy.tar.gz \
+            "https://github.com/aquasecurity/trivy/releases/download/v${TRIVY_VERSION}/trivy_${TRIVY_VERSION}_Linux-64bit.tar.gz"
+          tar -xzf /tmp/trivy.tar.gz -C /usr/local/bin trivy
+          trivy --version
+      - name: Run Trivy
+        run: |
+          trivy fs \
+            --scanners vuln \
+            --ignore-unfixed \
+            .
+      # Deep gitleaks scan (full git history). Same install pattern as
+      # ci.yml. `--redact` masks any matched secret in the log so we
+      # don't leak it via CI logs themselves.
+      - name: Install gitleaks
+        env:
+          GITLEAKS_VERSION: '8.21.0'
+          GITHUB_TOKEN: ${{ secrets.GITHUBCOM_TOKEN }}
+        run: |
+          curl -sfL \
+            -H "Authorization: Bearer ${GITHUB_TOKEN}" \
+            -o /tmp/gitleaks.tar.gz \
+            "https://github.com/gitleaks/gitleaks/releases/download/v${GITLEAKS_VERSION}/gitleaks_${GITLEAKS_VERSION}_linux_x64.tar.gz"
+          tar -xzf /tmp/gitleaks.tar.gz -C /usr/local/bin gitleaks
+          gitleaks version
+      - name: Run gitleaks (full history)
+        run: |
+          gitleaks detect \
+            --source . \
+            --redact \
+            --exit-code 1
 
   lighthouse-prod:
     # Skipped silently if the prod URL hasn't been configured yet.
@@ -44,7 +80,6 @@ jobs:
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: 'pnpm'
       - run: pnpm install --frozen-lockfile
       - run: pnpm exec lhci collect --url=${{ vars.LHCI_PROD_URL }} --numberOfRuns=3
       - run: pnpm exec lhci assert --config=./lighthouserc.js