chore: declare bench frappe-dependencies and carry v1.2.1 bump to develop

[Guru107]

[tool.bench.frappe-dependencies]

pyproject.toml had no [tool.bench.frappe-dependencies] section at all, so bench get-app / bench install-app ran no compatibility check — installing against an unsupported Frappe major would surface as a runtime failure rather than an install-time one. New modules need this declared.

[tool.bench.frappe-dependencies]
frappe = ">=15.0.0,<17.0.0"

The range covers v15 and v16, matching how the app is actually developed and tested (both benches are in use; the v1.2.x work was verified on each).

The commented-out frappe~=15.0.0 in [project].dependencies is left as is — that is a pip dependency deliberately delegated to bench, and a separate mechanism from this section.

Also included: 8140577

This PR is cut from release/v1, which was already one commit ahead of develop, so it also carries the v1.2.1 republish — __version__ = "1.2.1" and RELEASE_v1.2.0.md → RELEASE_v1.2.1.md. That brings develop in line with the v1.2.1 release; develop currently still reads 1.2.0.

Not included

• erpnext is not declared. The app hard-requires ERPNext for the Project and Item doctypes, so a matching erpnext = ">=15.0.0,<17.0.0" would normally sit alongside. Left out deliberately — only frappe was specified.
• CLAUDE.md still says "Frappe Framework: ~15.0.0 (managed by bench)", which understates the range now that v16 is declared supported.

Verification

• TOML parses; section resolves to {'frappe': '>=15.0.0,<17.0.0'}
• pre-commit run --all-files → exit 0, including the check toml hook
• No Python touched

🤖 Generated with Claude Code

[Guru107]

Superseded by #16. This PR was cut from release/v1, which was wrong on two counts: the change was committed directly to a release branch, and the PR dragged the unrelated v1.2.1 bump along with it. #16 is a dedicated chore/bench-frappe-dependencies branch off develop with just the one commit.