Add enterprise configuration client support

[svarlamov]

Summary

• add enterprise configuration metadata, validation, fetch response parsing, and API-key scoped cache storage
• apply enterprise overrides separately from user config for compatible policy fields
• bootstrap enterprise config during install-hooks and daemon startup, then refresh in a daemon worker
• fail enterprise API-key installs when the first config fetch cannot complete without a valid cache

Tests

• task fmt
• task lint
• cargo test --test config_fresh_test
• cargo test commands::install_hooks::tests --lib
• cargo test commands::config::tests --lib

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