fix: stop dependabot auto-merge from landing breaking majors

Root causes (this round):
- dependabot.yml had been overwritten to a minimal version with NO
  ignore rules -> major bumps allowed (typescript 7, eslint 10, tsparticles 4)
- main branch had NO branch protection -> 'gh pr merge --auto' merged
  even with failing CI
- auto-merge workflow had no check-run verification step

Fixes:
- Branch protection on main: required status check 'lint + typecheck +
  test + build' (strict) so auto-merge cannot land failing changes
- dependabot-auto-merge.yml: verify CI check-run conclusion == success
  (actions/github-script poll with timeout) before enabling auto-merge
- dependabot.yml: restore ignore rules for eslint/typescript/@tsparticles
  majors + eslint-config-next + eslint-plugin-react
- Rollback toolchain to known-good exact pins:
  typescript 6.0.3, eslint 9.39.5, @tsparticles/{react,engine,slim} 3.x
  (exact versions, no ranges dependabot can widen)
- Close dependabot PR #19 (tsparticles 4.4.0)

.github/dependabot.yml

@@ -5,6 +5,8 @@ updates:
     schedule:
       interval: "daily"
     open-pull-requests-limit: 10
+    labels:
+      - "dependencies"
     groups:
       production:
         dependency-type: "production"
@@ -16,3 +18,40 @@ updates:
         update-types:
           - "minor"
           - "patch"
+    ignore:
+      # ---- Toolchain pins: semver-major bumps break the lint/typecheck stack ----
+      # ESLint 10 dropped rule-context getFilename(); eslint-plugin-react (^7.37.x)
+      # peer range caps at eslint ^9.7 -> react/display-name crash at load.
+      - dependency-name: "eslint"
+        update-types: ["version-update:semver-major"]
+      # typescript-eslint 8.x peer range is ">=4.8.4 <6.1.0" -> TS 7 hard-refuses.
+      - dependency-name: "typescript"
+        update-types: ["version-update:semver-major"]
+      # @tsparticles v4 changed its exported API; the vendored SparklesCore from the
+      # Aceternity registry targets the v3 API (initParticlesEngine, IEffect.fill...).
+      # NOTE: dependabot `ignore` does NOT support wildcards (only `groups` does) —
+      # list each exact scoped package.
+      - dependency-name: "@tsparticles/react"
+        update-types: ["version-update:semver-major"]
+      - dependency-name: "@tsparticles/engine"
+        update-types: ["version-update:semver-major"]
+      - dependency-name: "@tsparticles/slim"
+        update-types: ["version-update:semver-major"]
+      # eslint-config-next majors follow Next.js majors and can pull incompatible
+      # plugin versions; framework majors are deliberate, not auto-bumps.
+      - dependency-name: "eslint-config-next"
+        update-types: ["version-update:semver-major"]
+      # eslint-plugin-react 8.x targets ESLint 10, which conflicts with the
+      # pinned eslint 9 (and the vendored components' validated toolchain).
+      - dependency-name: "eslint-plugin-react"
+        update-types: ["version-update:semver-major"]
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    groups:
+      actions:
+        patterns: ["*"]
+        update-types:
+          - "minor"
+          - "patch"