feat: upload video and screenshot attachments without a trace

[joris-gallot]

Seeing a video or screenshot in kinora required trace: 'on': isTraceAttachment gated uploads to zips, so with tracing off they stayed metadata pointing at a dead CI-runner path. Playwright doesn't couple them, our upload filter did.

Both ingest paths now filter by attachment kind, opt-in, ['trace'] by default:

reporter: [['@kinora/reporter', { project: { slug: 'web-app' }, uploadAttachments: ['trace', 'video', 'screenshot'] }]]

npx @kinora/cli upload results.json --project web-app --upload-attachments trace,video,screenshot

No on-failure filtering: screenshot: 'only-on-failure' and video: 'retain-on-failure' already decide what exists.

Two server bugs this uncovered, harmless while only zips were uploaded:

• The storage key hardcoded .zip, and /artifacts/* types responses from it, so a webm would have been served as application/zip. Extension now derives from the content type; trace keys keep their previous shape.
• Run-report urls were keyed by attachment name alone, so two toHaveScreenshot assertions (both attach actual) shared one url. Urls are now queued per name, in upload order.

Dashboard badges link to a.url when hosted, else fall back to the viewer's Attachments tab.

Refs #18.