Add Key Provider Access plugin

[GLGDLY]

Adds Key Provider Access to the official CLIProxyAPI plugin registry.

Repository: https://github.com/GLGDLY/key-provider-access
Latest release: https://github.com/GLGDLY/key-provider-access/releases/tag/v0.0.3

Capability:

• Enforces per-CPA-key allow and deny policies across OAuth profiles and API-backed upstream providers.
• Includes a management dashboard and profile-aware scheduler filtering.

Release evidence:

• v0.0.3 is a published, non-prerelease GitHub Release.
• The release includes checksums.txt.
• Platform archives are present for Linux amd64/arm64, Darwin amd64/arm64, Windows amd64/arm64, and FreeBSD amd64.
• The Linux amd64 archive checksum matches its checksums.txt entry.

Registry validation:

• registry.json parses successfully.
• key-provider-access is a unique, valid plugin ID.
• This PR changes only registry.json.

[GLGDLY]

note: this plugin is derived from @LTbinglingfeng https://github.com/LTbinglingfeng/key-model-access