chore: scope Dependabot to only packages we control (#2892)

## Summary
- Scoped Dependabot npm monitoring from the entire monorepo root (`/`)
to only the package directories we control
- Moved docusaurus monitoring to `/docsite` where the deps and lockfile
actually live (previously pointed at `/` where there are zero
`@docusaurus` entries in the root lockfile)
- Forked `@react-native/*` packages are now excluded — their
dependencies should stay in sync via upstream merges

**Monitored directories:**
- `/docsite`
- `/packages/react-native` (`react-native-macos`)
- `/packages/react-native-macos-init`
- `/packages/nx-release-version`
(`@react-native-macos/nx-release-version`)
- `/packages/virtualized-lists`
(`@react-native-macos/virtualized-lists`)

## Test plan
- [ ] Verify Dependabot picks up the new config on the next scheduled
run
- [ ] Confirm no PRs are opened for forked `@react-native/*` package
dependencies

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Saadnajmi

.github/dependabot.yml

@@ -1,18 +1,34 @@
-# Basic `dependabot.yml` file with
-# minimum configuration for three package managers
-
 version: 2
 updates:
   - package-ecosystem: "npm"
-    directory: "/"
+    directory: "/docsite"
+    schedule:
+      interval: "weekly"
+    groups:
+      all:
+        patterns:
+          - "*"
+
+  # Only monitor packages we control — forked @react-native/* packages
+  # should stay in sync via upstream merges.
+  - package-ecosystem: "npm"
+    directories:
+      - "/packages/react-native"
+      - "/packages/react-native-macos-init"
+      - "/packages/nx-release-version"
+      - "/packages/virtualized-lists"
     schedule:
       interval: "weekly"
     groups:
-      docusaurus:
+      all:
         patterns:
-          - "@docusaurus/*"
+          - "*"
 
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
       interval: "weekly"
+    groups:
+      all:
+        patterns:
+          - "*"