docs: fill journeydoc tutorials (content + capture spec + screenshots) (#72)

Filled in all 11 journeydoc tutorials with real prose (8 user-track +
3 admin-track), wired up the capture spec end-to-end, and committed
the 54 screenshots produced by a clean docs-capture run against the
local dev container.

Pages:
- user/01-first-launch — open Scholiq, walk the nav, confirm OR wiring
- user/02-create-course — Courses → Add Item dialog, save, open detail
- user/03-enrol-students — individual + Bulk-enrol from cohort/CSV
- user/04-assignments — publish brief, accept submissions, mark
- user/05-attendance — mark a session, roll-up to learner profile
- user/06-grading — grade entries → final grade + RS256 publish
- user/07-issue-certificate — verifiable credential + public verifier
- user/08-track-progress — Learner profile tabs (enrolments, grades,
  attendance, credentials, logs)
- admin/01-school-structure — programmes + cohorts + timetables
- admin/02-compliance-audit — signed audit-pack ZIP via Data exchange
- admin/03-admin-settings — register import, AI features, signing key

Capture spec: real flows via /apps/scholiq/{courses,enrolments,...}
with shoot() / dismissOverlays() / go() / captureCreateDialog()
helpers cloned from the decidesk pilot. Empty-state fallbacks where
seed data is not yet importable (OpenRegister register-import gap
openregister#1487).

Docs build verified locally: 11/11 capture tests pass, npm run build
in docs/ ends with [SUCCESS] (only the expected /privacy /terms /iso
footer warnings).

Author: rubenvdlinde