docs: comprehensive documentation overhaul

Add complete documentation structure:
- Frontend architecture documentation
- Database schema documentation
- Deployment guides (Docker, Traefik, Authentik, Environment)
- Development guides (Setup, Testing, Contributing, Quality Gates)
- Deployment architecture documentation
- Updated docs README with complete navigation

All new features and APIs are now documented.
Quality gates: docs only, no code changes

docs/templates/architecture.md

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+# Architecture Documentation Template
+
+Use this template when documenting system architecture.
+
+## System/Component Name
+
+## Overview
+
+Provide a high-level description of this system or component.
+
+## Architecture Diagram
+
+```
+[ASCII or Mermaid diagram showing components and relationships]
+```
+
+## Components
+
+### Component 1
+
+**Purpose:** What this component does
+
+**Responsibilities:**
+- Responsibility 1
+- Responsibility 2
+
+**Dependencies:**
+- Dependency 1
+- Dependency 2
+
+**Key Files:**
+- `path/to/file1.py`
+- `path/to/file2.py`
+
+### Component 2
+
+[Repeat for each component]
+
+## Data Flow
+
+Describe how data flows through the system.
+
+```
+[Step 1] → [Step 2] → [Step 3]
+```
+
+## Technology Stack
+
+| Component | Technology | Purpose |
+|-----------|-----------|---------|
+| Component 1 | Technology 1 | Purpose |
+| Component 2 | Technology 2 | Purpose |
+
+## Configuration
+
+Describe relevant configuration options.
+
+## Security Considerations
+
+List security considerations for this architecture.
+
+## Scaling Considerations
+
+Describe how this scales (or doesn't).
+
+## Related Documentation
+
+- [Link to related doc 1](link.md)
+- [Link to related doc 2](link.md)