SpringBrand 1.2.3 — Product README and Repository Icon

Docs-only release following the product README overhaul (#105).

• Rewrite README as a product introduction for marketplace listings: positioning, problem, advantages, examples, covered capabilities, and a one-prompt install section.
• Add a Simplified Chinese README (README.zh-CN.md) mirroring the English page, with a language switcher in both directions.
• Add the SpringBrand app icon (assets/springbrand-icon.png) to the README header.
• Bump VERSION and package manifests to 1.2.3 and synchronize Canonical Skills with their Distribution Mirrors; no Skill behavior changes.

Production identity: springbrand / SpringBrand, version 1.2.3, MCP https://connector.springbrand.ai/mcp. This release contains no development MCP identity in its shipping manifests.

Validation: all local test/validation scripts passed, including production identity and WorkBuddy release packaging. PR CI passed, including package-contract and native Codex CLI installation. Live provider availability, desktop OAuth and end-to-end task behavior are not claimed verified by these checks. No backend service deployment is included.

WorkBuddy immutable distribution has been published and verified:

• WorkBuddy ZIP
• Package manifest
• ZIP SHA-256: ddbcb325d1833bf03f33fbdc6e69e56e2c09524818d40e6ff0991afcfc1df980
• Production installation guide

Release publication CI passed, including R2 publication and public-byte verification.