feat(connect): AntSeed Connect with signed auto-deposit state

[gabrielpoca]

What

Adds the AntSeed Connect protocol and uses it to share the buyer's
auto-deposit status with a web app (the funding portal), signed by the seed
app. Stacked on top of auto-deposit-funding-portal.

A portal that only reads delegation on-chain (eth_getCode) cannot tell
"auto-deposit is off" from "the user turned it on but no funds have arrived
yet" (delegation lands lazily on the first deposit). Connect lets the seed app
report its real state { enabled, delegated } so the portal can show accurate
messaging.

Changes

• connect-core (new package): scope-driven request/response over the
  antseed://connect deep link, single EIP-191 personal_sign signature,
  response delivered in the redirect URL fragment. Scopes: address and
  auto-deposit (signed deterministic JSON { enabled, delegated }). Standalone,
  no @antseed/node dependency.
• CLI: antseed connect <link> with a consent prompt (--yes / --print).
• Desktop: antseed:// deep-link handler with cold-start buffering, parsing
  and signing in the main process (the renderer only shows the request and
  returns the decision), and a consent dialog.
• Seed-side auto-deposit state: enabled from config consent plus
  delegated read on-chain (eth_getCode against the EIP-7702 designator),
  signed into the response. The on-chain read reuses service-auto-deposit.
• Optional-plugin loading: the connect path does not hard-depend on
  service-auto-deposit. The CLI resolves the state reader from the plugins dir
  at runtime the same way loader.ts loads any plugin (moved to
  devDependencies); the desktop imports it lazily. A missing or stale plugin
  degrades to delegated: false while still reporting enabled from config,
  instead of failing at startup.
• Dark mode fix: re-map @antseed/ui --as-* tokens under
  body.dark-theme so the consent modal renders correctly in dark mode.

Testing

• connect-core: 37 unit tests (request-link validation incl. control-char
  injection, manifest parsing, response sign/verify round-trip, auto-deposit
  scope round-trip).
• Verified against the real CLI binary: antseed connect boots without the
  plugin installed, signs { enabled, delegated }, and the response verifies via
  verifyConnectResponse (recovered signer matches, auto-deposit value parses
  back). Graceful fallback confirmed when the plugin is absent/stale, and the
  reader is invoked for real when a current plugin is present.
• Desktop main builds and typechecks; the lazy import resolves from the desktop's
  bundled copy and the fallback preserves enabled.

Notes

• Base is auto-deposit-funding-portal (stacked), not main.
• The web funding-portal consumer is intentionally excluded from this PR.