feat: add /hive command to create Hive tasks from Telegram

[mainshivam]

Why?

The bot could only do HR flows (leave, WFH, petty cash), all of which need Frappe HR. Teams running Hive without HR or ERPNext had nothing they could use, and the app could not even be installed on such a site.

What?

A /hive command that creates a Hive Task from Telegram, with no HR dependency.

The flow: task title -> optional description -> start date -> end date -> project picker -> assignee picker (multi-select, tap to toggle) -> review -> create.

Projects come from open, non-archived Hive Project records. Assignees come from active Hive Member records of type Team, and are written to the standard _assign field, matching how Hive tracks them.

How?

Making this work without HR needed three supporting changes:

• BotConversation gains requires_employee (default True, so leave and WFH behave exactly as before) and required_doctypes. Commands are registered process-wide, so a site missing the owning app now gets a readable message instead of a traceback part way through a conversation.
• install.py skips custom fields whose doctype is absent. Previously a site without HR failed to install the app at all, because after_install created a field on Attendance Request. after_migrate re-runs it, so the field still appears if HR is installed later.
• The daily leave/WFH broadcasts and the monthly petty cash job return early when their doctypes are missing, rather than raising on schedule.

Also fixed

Every command in the Telegram menu showed the same description, "Apply for Work From Home".

Each conversation registers the same bound BotConversation.handle_command, so fn.__func__._description = description wrote to one shared function object and the last registration won for all of them. /ping was unaffected because it is a plain function. Descriptions now live in a dict keyed by command.

Tests

Adds bwh_bot/tests/test_hive.py, 15 tests, the first in this app:

• task creation with all fields, assignees landing in _assign
• skipping the description, creating with no assignees
• assignee toggle on and off
• end date before start rejected, empty title rejected
• back navigation, archived projects excluded
• the dependency gate, and a regression test for the description bug

Run with:

bench --site <site> run-tests --app bwh_bot --module bwh_bot.tests.test_hive

Verified on

A site with Hive but no HR and no ERPNext (frappe, raven, bwh_hive, drive, bwh_bot), plus a site with HR installed to confirm leave and WFH are unchanged.