[DISCORDSH] Design Supabase Vault schema for GitHub PAT storage

[h0lybyte]

Parent

Part of #7849

Description

Design the Supabase Vault schema for storing GitHub Personal Access Tokens per-org and per-repo. Define how the bot retrieves and rotates secrets at runtime via vault.create_secret() / vault.read_secret().

Acceptance Criteria

• Vault table/schema design documented
• Per-org and per-repo PAT scoping supported
• Secret rotation strategy defined