import: chat & messaging batch (6 scripts)

[Aybook]

First import batch. Pulls six chat and messaging scripts from upstream luadch/scripts (dead since 2022-08), each at its highest version, BOM-stripped where the upstream file shipped one, prefixed with a provenance header pointing back at `docs/IMPORT_NOTES.md`.

Scripts in this PR

Script	Upstream version	Function
`bot_advanced_chat`	v0.5 (multi)	Advanced chat bot with history, members table, pm2op forward
`etc_messenger`	v0.4 (english)	Bot-style PM messaging with delivery queue
`etc_blackboard`	v0.2 (multi)	Shared bulletin board, persistent
`etc_wunschbrett`	v0.2 (multi)	Wishlist / request forum, persistent
`etc_mainecho`	v0.3 (english)	Main-chat echo with exclude-trigger table
`ptx_poll_bot`	v3.0 (english)	Polling / voting bot, persistent

Layout

Files mirror the hub's `scripts/` directory layout so wholesale install (`cp -r repo/scripts/* hub/scripts/`) just works:

• `scripts/.lua`
• `scripts/lang/.lang.{en,de}` for the localised ones
• `scripts/data/_<...>.tbl` for state files (most scripts)
• `scripts//...` for scripts using a script-named state subdir (etc_blackboard, etc_wunschbrett)

State files ship empty / default so the directories exist at first save.

Normalisation

`etc_wunschbrett` upstream literally set `scriptname = "etc_wunschbrett_v0.2"` (with version baked into the identifier), and the lang files matched (`etc_wunschbrett_v0.2.lang.{en,de}`). On import, normalised to `etc_wunschbrett` plus matching lang filenames; comment in the file documents the change.

Audit

• Lua 5.4 patterns checked across the batch: zero hits for `setfenv` / `getfenv` / `loadstring` / `unpack` / `module(...)` / `os.execute` / `io.popen` / `debug.` / 1-arg `os.difftime` / `math.atan2` / `math.pow` / `math.log10`. The luadch sandbox API kept users on `hub.` / `cfg.` / `util.` so direct stdlib usage is rare.
• BOMs at file head: present on all six upstream files; stripped on prepend so the surviving content has the provenance header at offset 0 with no mid-file BOM.

Test plan

• Drop scripts into `d:\Projekte\luadch\build\install\luadch\scripts\ with their lang/data assets, run smoke harness against [\luadch-ng/luadch`](https://github.com/luadch-ng/luadch) v3.1.1: 10 / 10 PASS, including the "no script errors in log" gate. All six scripts loaded cleanly under the empty-`_ENV` sandbox.
• Manual functional smoke per script (chat command exercise) - deferred to a follow-up if needed; the load-clean check is the floor for this batch.

Out of scope

• Functional bug fixes to upstream issues touching these scripts (none of the 19 open upstream issues map to this batch's six scripts).
• Behaviour changes to the scripts themselves; pure import + provenance + minimal normalisation only.

Refs the import-pass triage in `docs/IMPORT_NOTES.md`.