Add direct private key login option (UserWallet-style)

[Stephen-Thomson]

Description of Changes

• Adds a third login type ("direct private key") alongside WAB and mnemonic-advanced, using SimpleWalletManager with no password, recovery key, or profile support
• New Greeter flow accepts either a mnemonic phrase or raw hex private key, with "Generate Random" options for both
• Security page shows "Private Key Management" UI in direct-key mode (reveal recovery phrase / private key / both)
• Profile-dependent features (sidebar profiles, internal transfers, privileged identity key) are cleanly hidden in direct-key mode
• Key material persisted to localStorage so it survives page reloads and can be revealed from Security
• Message Box configuration UX improved with inline setup prompts

Linked Issues / Tickets

None

Testing Procedure

Manually tested:

• WAB login flow works identically to before

• Mnemonic-advanced login flow works identically to before

• Direct-key login with mnemonic (12/24 word) authenticates successfully

• Direct-key login with hex key authenticates successfully

• Generate Random works for both mnemonic and hex modes

• Public key (66 chars) rejected with clear error message

• All dashboard pages load without errors in direct-key mode

• Security page reveals recovery phrase and private key correctly

• Profiles hidden from sidebar menu in direct-key mode

• Internal Transfer tab hidden in Payments in direct-key mode

• Privileged identity key section hidden in direct-key mode

• Login type persists across app restarts via snapshot

• Build passes with no type errors

• I have added new unit tests

• All tests pass locally

• I have tested manually in my local environment

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have updated CHANGELOG.md with my changes
• I have run npm run doc and npm run lint one final time before requesting a review
• I have fixed all linter errors to ensure these changes are compliant with ts-standard
• I have run npm version patch so that my changes will trigger a new version to be released when they are merged