Migrate to new Gitea instance (gitea.wbd-rd.nl)

- Update all submodule URLs from gitea.centraal.wbd-rd.nl to gitea.wbd-rd.nl
- Add settler as proper submodule in .gitmodules
- Add agent skills, function anchors, decisions, and improvements
- Add Docker configuration and scripts
- Add manuals and third_party docs
- Update .gitignore with secrets and build artifacts
- Remove stale .tgz build artifact

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

.agents/decisions/DECISION_TEMPLATE.md

@@ -0,0 +1,36 @@
+# DECISION-YYYYMMDD-<slug>
+
+## Context
+- Task/request:
+- Impacted files/contracts:
+- Why a decision is required now:
+
+## Options
+1. Option A
+- Benefits:
+- Risks:
+- Rollout notes:
+
+2. Option B
+- Benefits:
+- Risks:
+- Rollout notes:
+
+## Decision
+- Selected option:
+- Decision owner:
+- Date:
+- Rationale:
+
+## Consequences
+- Compatibility impact:
+- Safety/security impact:
+- Data/operations impact:
+
+## Implementation Notes
+- Required code/doc updates:
+- Validation evidence required:
+
+## Rollback / Migration
+- Rollback strategy:
+- Migration/deprecation plan: