Feature: support multiple OWS wallets and active wallet selection

[realproject7]

Context

PlotToon is adding multi-wallet support for OWS wallets. The same user need also exists in plotlink-ows: users may want to maintain multiple local OWS wallets on one machine and switch which wallet is active for publishing, dashboard, royalty, and AI writer/account operations.

Current plotlink-ows behavior appears to be single-wallet oriented: several routes call listAgentWallets() and then choose the first wallet whose name starts with plotlink-writer. That works for one wallet, but it is ambiguous once multiple OWS wallets exist.

Scope

• Add an active OWS wallet selection model for plotlink-ows.
  • Persist selected wallet identity locally.
  • Store/display non-secret metadata only: wallet name/id, normalized address, source/label.
  • Do not expose passphrases, private keys, wallet file contents, or sensitive local paths.
• Replace first-plotlink-writer lookup behavior with explicit active-wallet selection in wallet-bound routes.
• Add wallet switcher UI for local OWS wallets.
• Ensure these surfaces use the active wallet:
  • /api/wallet
  • /api/wallet/create
  • publish preflight and publish routes
  • cover/plot image upload signatures if wallet-signed
  • storyline update signing
  • dashboard/balance display
  • royalty claim flow
  • AI writer registration and owner/binding flows
• Keep single-wallet users working without extra setup.
• Add legacy behavior for existing installs: if exactly one recognized OWS wallet exists, select it automatically; if multiple exist and no active wallet is selected, prompt the user to choose.

Acceptance Criteria

• A user can create or discover more than one local OWS wallet and select the active one.
• Publishing and signing use the selected wallet, not the first wallet matching a prefix.
• Dashboard/account/royalty/AI writer views reflect the selected wallet.
• Switching wallets does not mix story/dashboard/publish context.
• Existing one-wallet installs remain usable.
• Tests cover at least two fake wallet identities and active-wallet switching.

Security Notes

• Use fake addresses in tests and public PR text.
• Never log or render private keys, seed material, passphrases, wallet file contents, or sensitive local paths.