chore: migrate submodules to public repos, rework docs and CI/CD

- Update .gitmodules: ztools, silo, and OndselSolver now reference
  public git.kindred-systems.com URLs instead of internal Gitea
- Merge OndselSolver numerical solver with ML solver scaffolding
  into unified kindred/solver repository
- Rewrite README.md for conciseness
- Add docs/CI_CD.md with full pipeline documentation
- Rework CI/CD workflows for public dockerized runners
- Add multi-platform release builds (Linux, macOS, Windows)
- Release workflow triggers on v* tags only
- Update docs/REPOSITORY_STATE.md and docs/INTEGRATION_PLAN.md

.gitmodules

@@ -1,6 +1,6 @@
 [submodule "src/3rdParty/OndselSolver"]
 	path = src/3rdParty/OndselSolver
-	url = https://gitea.kindred.internal/kindred/ondsel.git
+	url = https://git.kindred-systems.com/kindred/solver.git
 [submodule "tests/lib"]
 	path = tests/lib
 	url = https://github.com/google/googletest
@@ -12,7 +12,7 @@
 	url = https://github.com/FreeCAD/AddonManager.git
 [submodule "mods/ztools"]
 	path = mods/ztools
-	url = https://gitea.kindred.internal/kindred/ztools-0065.git
+	url = https://git.kindred-systems.com/forbes/ztools.git
 [submodule "mods/silo"]
 	path = mods/silo
-	url = https://gitea.kindred.internal/kindred/silo-0062.git
+	url = https://git.kindred-systems.com/kindred/silo.git