Enable Dependabot for npm + cargo + pip with grouped weekly PRs

[kilodesodiq-arch]

Problem Statement. .github/dependabot.yml is intentionally disabled (configured
with open-pull-requests-limit: 0). Many library upgrades are deferred.

Technical Context.
.github/dependabot.yml.

Expected Outcome. A new .github/dependabot.yml enables npm, cargo, pip, github-actions
ecosystems. Grouped weekly PRs (@dependabot squash).

Acceptance Criteria.

• PRs are auto-titled per ecosystem.
• A renovate.json mirror exists for those who prefer Renovate.

Files or modules likely to be affected.
.github/dependabot.yml,
new .github/renovate.json (alternative).

Difficulty. Easy
Estimated effort. S

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Backlog item #94 from `docs/maintainer-issue-backlog.md.

[Ayinkx1]

Hi i would like to work on this issue please assign to me
I can do it perfectly

[grantfox-oss]

🦊 GrantFox — @Ayinkx1 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #302)
2. Your PR will be reviewed by the ChainForgee maintainers

Good luck! Track your progress on GrantFox.