chore: datafactory install pins → PyPI floor (views-datafactory>=1.9.0)

[Polichinel]

views-datafactory is public and on PyPI as of v1.9.0 — pip install views-datafactory.

• 27 model requirements.txt: git+...@development → views-datafactory>=1.9.0 (matches the existing views-r2darts2>=0.1.0 house style in the same files). Fresh model envs no longer need GitHub access to resolve the dependency.
• README: adds a datafactory-backend paragraph to the config_queryset.py section — the backend was documented in 12+ per-model READMEs but never in the front door — linking the new model consumer quickstart.
• Register C-36 notes: remediation command updated to the PyPI pin.

Deliberately excluded: postprocessors/un_fao/* install lines — those files carry the in-flight land_gaul/feature_frame migration in the maintainer's working tree; fold the one-line pin change into that commit instead (requirements.txt:1, README.md:73, configs/config_queryset.py:21).

Part of the cross-repo tagged-release rollout (sibling PR: views-pipeline-core#315).

🤖 Generated with Claude Code

[Polichinel]

Review — sound, approve with one recommended change

Verified the claims against the repo:

• ✅ views-datafactory 1.9.0 is live on PyPI (checked the PyPI API — latest release, present). Since CI and fresh envs install published packages, this is what makes the floor pin safe. Cleared.
• ✅ Scope correct — 27 model requirements.txt (git+…@development → PyPI pin), README, register; un_fao deliberately excluded (confirmed — it still carries the git pin locally).
• ✅ README front-door "Data backends" paragraph fills a real gap (datafactory backend was only ever documented in per-model READMEs).
• ✅ Register update: the datafactory-readiness Fix: command correctly moves to the PyPI pin.

Recommended change before merge

The new pin is unbounded (views-datafactory>=1.9.0), unlike its siblings: views-hydranet>=0.1.0,<1.0.0 and views-r2darts2>=1.0.0,<2.0.0 both cap the major. Suggest views-datafactory>=1.9.0,<2.0.0 across the 27 files to match house style and prevent a future breaking 2.0 being pulled in silently. (Cosmetic follow-on: the PR body cites views-r2darts2>=0.1.0, but the actual r2darts pin is >=1.0.0,<2.0.0.)

The deferred un_fao pin is now handled

Per this PR's note, the un_fao datafactory pin (requirements.txt, config_queryset.py install string, README) has been folded into the in-flight land_gaul/feature_frame working-tree change, pinned to views-datafactory>=1.9.0,<2.0.0. So un_fao lands with the rest — just via that branch, not this PR.

Minor note

The diff edits 8 temporary_*/requirements.txt (rusty_bucket constituents / dwarf scaffolds). A requirements pin isn't the hp-config content parallel sessions tune, so fine — flagging as a conscious inclusion.