feat(docs): restructure documentation with new framework and templates

- Archive old docs to docs-old/ for reference
- Create new top-down documentation structure:
  * Platform Overview: purpose, audience, product structure
  * Components: individual platform components (Forgejo, Kubernetes, Backstage)
  * Getting Started: onboarding and quick start guides
  * Operations: deployment, monitoring, troubleshooting
  * Governance: ADRs, project history, compliance
- Add DOCUMENTATION-GUIDE.md with writing guidelines and templates
- Add component template (TEMPLATE.md) for consistent documentation
- Simplify root README and move technical docs to doc/ folder
- Update test configuration:
  * Exclude legacy content from markdown linting
  * Relax HTML validation for theme-generated content
  * Skip link checking for legacy content in test:links
  * Keep 'task test' clean for technical writers (100% pass)
  * Add 'task test:full' with comprehensive link checking
- Update home page with corrected markdown syntax
- Fix internal links in archived content

BREAKING CHANGE: Documentation structure changed from flat to hierarchical top-down approach

content/en/docs-old/architecture/highlevelarch.md

@@ -0,0 +1,79 @@
+---
+title: "High Level Architecture"
+linkTitle: "High Level Architecture"
+weight: 1
+description: >
+  Interactive high-level architecture overview of the Enterprise Development Platform
+---
+
+This document describes the high-level architecture of our Enterprise Development Platform (EDP) system.
+
+## Interactive Architecture Diagram
+
+{{< likec4-view view="otc-faas" project="architecture" title="Enterprise Development Platform - OTC FaaS Deployment Architecture" >}}
+
+{{< alert title="Interactive Diagram" >}}
+The diagram above is interactive when viewed in a compatible browser.
+You can click on components to explore the architecture details.
+
+**Note:** The interactive diagram requires the LikeC4 webcomponent to be generated.
+See the [setup instructions]({{< ref "/docs-old/architecture/setup" >}}) for details.
+{{< /alert >}}
+
+## Architecture Overview
+
+The Enterprise Development Platform consists of several key components working together to provide a comprehensive development and deployment environment.
+
+### Key Components
+
+1. **OTC Foundry** - Central management and orchestration layer
+2. **Per-Tenant EDP** - Isolated development environments for each tenant
+3. **FaaS Environment** - Function-as-a-Service deployment targets on Open Telekom Cloud
+4. **Cloud Services** - Managed services including databases, storage, and monitoring
+
+### Deployment Environments
+
+- **Development Environment** (`*.t09.de`) - For platform team development and testing
+- **Production Environment** (`*.buildth.ing`) - For production workloads and tenant services
+
+## Component Details
+
+The interactive diagram above shows the relationships between different components and how they interact within the system architecture. You can explore the diagram by clicking on different elements to see more details.
+
+### Infrastructure Components
+
+- **Kubernetes Clusters** - Container orchestration using OTC CCE (Cloud Container Engine)
+- **ArgoCD** - GitOps continuous deployment and application lifecycle management
+- **Forgejo** - Git repository management and CI/CD pipelines
+- **Observability Stack** - Monitoring (Prometheus, Grafana), logging (Loki), and alerting
+
+### Security and Management
+
+- **Keycloak** - Identity and access management (IAM)
+- **OpenBao** - Secrets management (Hashicorp Vault fork)
+- **External Secrets Operator** - Kubernetes secrets integration
+- **Crossplane** - Infrastructure as Code and cloud resource provisioning
+
+### Developer Experience
+
+- **Backstage** - Internal developer portal and service catalog
+- **Forgejo Actions** - CI/CD pipeline execution
+- **Development Workflows** - GitOps-based inner and outer loop workflows
+
+## Setup and Maintenance
+
+To update or modify the architecture diagrams:
+
+1. Edit the `.c4` files in `resources/edp-likec4/`
+2. Regenerate the webcomponent:
+
+   ```bash
+   cd resources/edp-likec4
+   npx likec4 codegen webcomponent \
+     --webcomponent-prefix likec4 \
+     --outfile ../../static/js/likec4-webcomponent.js
+   ```
+
+3. Commit both the model changes and the regenerated JavaScript file
+
+For more information, see the [LikeC4 Integration Guide]({{< ref "/docs-old/architecture/setup" >}}).