import: mod-tools batch (4 plugins, etc_NewPasswords v3.1.x adapt)

[Aybook]

Second import batch. Four mod / admin-tool plugins, each in its own subfolder per the layout that landed in #2.

Plugins in this PR

Plugin	Upstream	Function	Notes
`cmd_mainclear`	v0.02 (german)	Clears main chat by broadcasting blank lines	Tiny
`cmd_pm2offliners`	v0.8 (multi3)	Send PM to offline users with delivery confirmation on next login	Lang en/de/sv. Upstream issues #29, #30, #41 are not fixed here (import-first discipline)
`etc_levelcheck`	v0.1 (english)	Reports caller's user level via PM	Debug/admin one-liner
`etc_NewPasswords`	v0.4 (multi3)	Auto-generates a new password for ineligible users on next login, disconnects them with the new password	Lang en/de/sv. v3.1.x compat adapt below.

etc_NewPasswords v3.1.x adapt

The upstream pattern - `util.loadtable("cfg/user.tbl") + util.savearray()` - is incompatible with the AES-256-GCM encrypted `user.tbl` introduced in luadch-ng v3.1.x (Phase 7f). Direct read returns nil (Lua source parser sees ciphertext); direct write would destroy the encrypted file with plaintext.

Switched both touch-points to the proper hub API:

• Password change path (`onLogin` listener): `target:setpassword(new_pw)` instead of mutating `user_tbl[k].password` and writing the file back. `setpassword` validates against `_regex.reguser.password`, mutates the in-memory profile, and calls `cfg.saveusers()` which encrypts on disk.
• Enumeration path (`onStart`): `hub.getregusers()` instead of `util.loadtable("cfg/user.tbl")`. Returns the live in-memory `_regusers` array, no file I/O.
• Dropped now-unused `hub_reloadusers` and `util_savearray` table-lookups; `user_db` constant removed.

Compat note is documented in the file's provenance header so future maintainers know why this script diverges from the upstream version.

Audit

• Lua 5.4 patterns checked across the batch: zero hits.
• BOMs at file head: stripped where upstream shipped them.
• No `os.execute` / `io.popen` / `debug.*` / `module(...)` etc.

Test plan

• Drop both batch import: chat & messaging batch (6 scripts) #1 (PR import: chat & messaging batch (6 scripts) #1, merged) and this batch into a fresh hub install, run the `luadch-ng/luadch` v3.1.1 smoke harness: 10 / 10 PASS including "no script errors in log". The etc_NewPasswords onStart runs against the live regusers table, so the v3.1.x adapt is exercised at boot.
• Functional test of the `+newpw` command path on a real hub - deferred; the load-clean check is the floor for this batch.

Out of scope (deferred)

• Functional bug fixes for upstream issues fix(ptx_freshstuff): switch dat-file loading to util.loadtable #29 / ptx_RSSFeedWatch: 4 require() calls break post-luadch-#206 sandbox #30 / #41 (cmd_pm2offliners). They'll get a fresh sweep against this repo after the import phase is done, analog to our luadch-ng/luadch upstream-triage interludes.