Attachments: several files when creating an issue, 10 MiB per file (0.1.16) - #14

Why

• The New issue dialog had no way to attach anything: a person created the issue, opened it, then attached. Only the bug report page took screenshots up front.
• 2 MiB per file refused full-page and high-density screenshots.

What

• New issue dialog: choose several files, paste (also while typing the description) or drop; previews with remove; refused files (type, size, count) show their reason next to the area. On create the issue is made first, then files upload one by one with progress. If some uploads fail, the dialog stays in a result state naming the issue and the files not attached, with a link to the issue; there is no retry that could create a second issue.
• Shared implementation: the report page and the dialog use one hook and one preview grid (web/src/features/issues/pending-attachments.tsx); pure parts in web/src/model/issues.ts.
• Limit: 10 MiB per file (was 2 MiB), still 10 files per issue and the same media types. domain.AttachmentMaxBytes is the single server constant; migration 015 widens the column CHECK; the SPA constant and copy follow.

Trade-off

Attachments are bytea rows. At 10 MiB each upload and download is held in memory once, and an issue can hold 100 MiB. Recorded in design/README.md.

Verification

• go vet ./cmd/...; go test -count=1 ./cmd/... against a disposable Postgres 17, including the new TestAttachmentSizeBoundary (exactly 10 MiB stored, one byte more refused) and the migration count.
• web: tsc --noEmit, bun test src.
• Browser against the mock API, 1280×800: Create visible with no files; 3 images selected → 3 previews; GIF and an 11 MiB PNG refused with reasons, a 6 MiB PNG accepted; one removed; image pasted into the description became an attachment with no text inserted; created issue showed the 4 attachments. Forced a 500 on the second upload → result state listed that file and linked the issue. /report still adds and refuses files.
• Not verified: the deployed installation; the mobile bottom-sheet layout; a screen reader.