* feat(den): add org-managed llm provider library
Let Den admins curate shared providers and models with encrypted credentials, then let the app connect through the existing add-provider flow. This keeps org-wide model access consistent without requiring per-user OAuth setup.
* docs(den): prefer longer db encryption keys
* fix(den): pass db encryption key through local dev
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Co-authored-by: src-opn <src-opn@users.noreply.github.com>
