docs: update stale base-org references in README to base

[golldyck]

Problem

The org moved from base-org to base, but the root README.md still references the old org in eight places: the contract-deployments link on line 7, and seven shield badge URLs on lines 11-15 and 27-28 (contributors, commit activity, stars, repo size, license, open PRs, open issues). The badges render images for a path that no longer exists, and the deployments link resolves to the defunct org.

Fix

Replaced every base-org/contracts and base-org/contract-deployments occurrence with base/contracts and base/contract-deployments. No other files in the repo carry the stale org name.

Changes

• README.md — Updated the contract-deployments link (line 7) and all seven shield badge URLs (lines 11-15, 27-28) to use the current base GitHub org

Testing

• Ran `grep -rn "base-org" .` on the whole repo after the fix — no remaining occurrences
• Verified each updated URL resolves (badges: `img.shields.io/github/*/base/contracts`; link: `github.com/base/contract-deployments`)
• Confirmed the fix matches the enumeration in the reporter's issue (line 7, lines 11-15, lines 27-28)

Closes #248

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2