feat(web): add copy actions for upstreams and model aliases

[yyyr-p]

Summary

Both list pages gain a copy action next to edit, so a working upstream or model alias can be duplicated without recreating every field by hand.

Upstreams open a new /dashboard/providers/upstreams/:id/copy route that reuses the existing editor in create mode, seeded from the source record with a fresh id, a {{name}} copy name, and a distinct hue. structuredClone isolates every nested field so editing the copy can't mutate the source.

The credential is the one field that isn't a straight copy, and it follows the provider kind:

Kind	On copy
custom (API key), azure, ollama	Carry the stored key over through the editor's "leave blank to keep" contract — the secret field stays blank and on save the source's key is kept without re-entering it.
copilot, codex, claude-code	Reset to the blueprint shape; OAuth tokens are minted by the exchange and aren't valid as a second grant, so carrying them would ship a dead credential.

Model aliases reuse the existing dialog in a new copy mode that seeds from the source with a {{name}} copy name but saves through the create endpoint, producing a second alias rather than overwriting. The dialog's mode (create | edit | copy) replaces the old record ? edit : create boolean so duplicate detection and the save target can tell the three apart.

New en and zh-Hans strings carry the copy labels, name suffix, dialog title, and document title (the two locales stay structurally equivalent); routes.ts registers the route and document-title-sync maps its path to the title.

Test Plan

• pnpm run verify — every stage passes except five tests that fail identically on the feature commit before this PR (copilot-device-flow_test.tsx ×4 and oauth-authorize-url_test.tsx ×1, all timing/poll-count expected 1, received 0), so they are pre-existing and unrelated to this change.