refactor: source the API origin from @canup/contracts (single constant)

[cescox]

The default API origin (https://canup.link) was defined in three places under two names — DEFAULT_API_URL in cli/constants.ts, an inline DEFAULT_API_URL in ui/internal/api-client.ts, and DEFAULT_CANUP_URL in @canup/contracts. This collapses them to one definition.

• Both packages now import { DEFAULT_CANUP_URL } from '@canup/contracts' and use it directly; the CLI also takes API_VERSION from there.
• cli/constants.ts is deleted (both its exports now live in the contract); the inline ui const is gone.
• Bumps @canup/contracts to ^0.2.1, the release that adds the constants.

One canonical origin, no drift between client and contract. Net −5 lines.

Verification

test (358 cli + 115 ui), lint, typecheck, build — all green. No DEFAULT_API_URL or hardcoded origin remains in source.

[github-actions]

Coverage Report for @canup/ui (packages/ui)

Status	Category	Percentage	Covered / Total
🔵	Lines	98.38% (🎯 95%)	183 / 186
🔵	Statements	98.07% (🎯 95%)	204 / 208
🔵	Functions	98.07% (🎯 95%)	51 / 52
🔵	Branches	96.06% (🎯 85%)	122 / 127

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
packages/ui/src/internal/api-client.ts	93.33%	100%	100%	91.66%	24

Generated in workflow #41 for commit 9f3e508 by the Vitest Coverage Report Action

[github-actions]

Coverage Report for @canup/cli (packages/cli)

Status	Category	Percentage	Covered / Total
🔵	Lines	98.9% (🎯 95%)	1082 / 1094
🔵	Statements	98.68% (🎯 95%)	1125 / 1140
🔵	Functions	98.46% (🎯 95%)	193 / 196
🔵	Branches	92.45% (🎯 85%)	515 / 557

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
packages/cli/src/api-client.ts	98.03%	95.23%	100%	97.87%	195
packages/cli/src/auth/perform-login.ts	100%	83.33%	100%	100%

Generated in workflow #41 for commit 9f3e508 by the Vitest Coverage Report Action