Initialize evermore platform docs repo #23

Create a new lightweight git repo at evermore/platform/ to hold umbrella documentation and conventions shared across the three module repos. This is a docs/governance repo, not a code repo.

Initial scaffold:

• platform/CLAUDE.md — points AI assistants at architecture doc, names the four sibling repos
• platform/README.md — what Evermore is, the philanthropic origin via the design-partner shelter, the subscription vision
• platform/docs/ — empty directory ready for architecture, auth-flow, subscriptions, module-template docs
• platform/docs/adr/ — empty directory for cross-cutting ADRs

Acceptance Criteria

• evermore/platform/.git exists and is a clean git repo
• platform/CLAUDE.md exists with concise umbrella guidance and links to per-repo CLAUDE.md files
• platform/README.md describes the Evermore platform and the four sibling repos
• platform/docs/ and platform/docs/adr/ directories exist
• Initial commit lands on main

Migrated from Beads prof-iqb.2.