Phase 1: CKPool build infrastructure

Forks CKPool-solo at upstream commit cfb0f83b (v1.0) via a multi-stage
Docker build, with an env-driven entrypoint that renders ckpool.conf from
a template. The pinned commit already includes every fix referenced in
Bassin issue #29 (workbase_id double increment, extended low-power
timeouts, configurable dropidle, vardiff burst handling).

No patches are applied yet — the patches/ directory holds the workflow
and build wiring so Kamado-specific patches can be added incrementally.

Build is portable across aarch64/x86_64: yasm is intentionally omitted
so CKPool falls back to its C SHA256, and CFLAGS override drops upstream's
default -march=native. Runtime image ships ckpool and ckpmsg for socket
debugging; share logging (-L) is enabled by default.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

LICENSE

@@ -0,0 +1,22 @@
+Kamado Pool
+Copyright (C) 2026 Kamado Pool contributors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+---
+
+This project is built on top of CKPool by Con Kolivas, which is itself
+licensed under GPL-3.0. See https://bitbucket.org/ckolivas/ckpool for
+the upstream source. The full GPL-3.0 text is available at:
+https://www.gnu.org/licenses/gpl-3.0.txt