Configure monorepo build: unified CI, local deps, .dockerignore

- Dockerfiles use monorepo root as build context
- common/ and core/ installed as local packages (no git+https)
- Client tarball built from local client/ dir
- Unified CI with change detection: common/core -> rebuild both
- Per-repo CI workflows removed

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

.dockerignore

@@ -0,0 +1,8 @@
+.git
+.gitea
+**/.env
+**/.env.gpu
+**/__pycache__
+**/.pytest_cache
+**/*.pyc
+test/