feat(eslint+ci): R40 boundary rule for @sentry/* + R31 sendDefaultPii grep gate

Adds two flat-config blocks to core-eslint/base.js: (1) repo-wide
no-restricted-imports for @sentry/* with the R40 message, (2) an
allowlist override for the only paths permitted to import the Sentry
SDK directly — core-shared/instrumentation/sentry/**, the bind-sentry
DI files, the no-sentry test guards, and apps' instrumentation* /
next.config / vite.config / sentry.*.config files. Patterns use
**/-prefix so they match whether ESLint runs from the repo root or
from inside a sub-package.

Also adds the standard `argsIgnorePattern: "^_"` config (used
throughout the repo) and a Node-globals override for *.mjs/*.cjs/*.js
and *.config.{ts,tsx} so withSentryConfig in next.config.mjs lints
clean. Required adding `globals` as a core-eslint dep.

Adds .github/workflows/sentry-pii-guard.yml — a lightweight CI step
that fails any PR introducing `sendDefaultPii: true` (R31). Excludes
node_modules / dist / .next / .turbo from the grep so vendored SDK
JSDoc examples don't false-positive.

Pre-existing lint nits cleared as part of getting `pnpm lint` green:
- core-testing define-contract-suite.test.ts: void the unused
  receivedTracer (mirrors the next test's pattern)
- marketing-pages bind-dev-seed.ts: drop unused MockSiteSettingsRepository
  import
- marketing-pages get-site-settings.use-case.ts: drop the now-redundant
  eslint-disable for `_input`

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/sentry-pii-guard.yml

@@ -0,0 +1,28 @@
+# R31 — block sendDefaultPii: true from ever landing.
+#
+# This is a defense-in-depth gate: the privacy posture is also enforced by
+# the centralized init helpers in core-shared/instrumentation/sentry/, but
+# this grep makes any drift impossible to merge.
+
+name: Sentry PII guard (R31)
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  pii-guard:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Verify sendDefaultPii is never true
+        run: |
+          if grep -RIn --include='*.ts' --include='*.tsx' --include='*.mjs' --include='*.cjs' --include='*.js' \
+              --exclude-dir=node_modules --exclude-dir=.next --exclude-dir=dist --exclude-dir=.turbo \
+              -E 'sendDefaultPii\s*:\s*true' \
+              packages/ apps/; then
+            echo "::error::R31 violation — sendDefaultPii: true is forbidden anywhere in the repo."
+            exit 1
+          fi
+          echo "OK — no sendDefaultPii: true detected."