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/api-endpoint.md

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+# API Endpoint Documentation Template
+
+Use this template when documenting API endpoints.
+
+## Endpoint Group Name
+
+Brief description of what this group of endpoints does.
+
+### Authentication
+
+Describe authentication requirements (e.g., "Requires valid session cookie").
+
+---
+
+## METHOD /path/to/endpoint
+
+**Description:** What this endpoint does.
+
+### Request
+
+#### Headers
+
+| Header | Required | Description |
+|--------|----------|-------------|
+| `Authorization` | Yes/No | Description |
+| `Content-Type` | Yes/No | Description |
+
+#### Query Parameters
+
+| Parameter | Type | Required | Description |
+|-----------|------|----------|-------------|
+| `param_name` | `string` | Yes/No | Description |
+
+#### Request Body
+
+```json
+{
+  "field_name": "string",
+  "field_name": "number"
+}
+```
+
+| Field | Type | Required | Description |
+|-------|------|----------|-------------|
+| `field_name` | `string` | Yes/No | Description |
+
+### Response
+
+#### Success (200 OK)
+
+```json
+{
+  "field_name": "value",
+  "field_name": "value"
+}
+```
+
+#### Error Responses
+
+**400 Bad Request**
+```json
+{
+  "detail": "Error message"
+}
+```
+
+**401 Unauthorized**
+```json
+{
+  "detail": "Authentication required"
+}
+```
+
+### Example
+
+#### Request
+```bash
+curl -X METHOD http://api.example.com/path/to/endpoint \
+  -H "Content-Type: application/json" \
+  -H "Cookie: session=your_session_cookie" \
+  -d '{
+    "field_name": "value"
+  }'
+```
+
+#### Response
+```json
+{
+  "field_name": "value"
+}
+```
+
+---
+
+## METHOD /path/to/another/endpoint
+
+[Repeat the same structure for each endpoint]

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)

docs/templates/feature-doc.md

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+# Feature Documentation Template
+
+Use this template when documenting a new feature.
+
+## Feature Name
+
+## Overview
+
+Provide a 1-2 sentence description of what this feature does and why it exists.
+
+## How to Use
+
+### Prerequisites
+
+List any prerequisites (e.g., must be logged in, must have project created).
+
+### Step-by-Step Guide
+
+1. **Step 1**: Description of first step
+   - Details
+   - Screenshots if applicable
+
+2. **Step 2**: Description of second step
+   - Details
+
+3. **Step 3**: Description of third step
+   - Details
+
+## Screenshots
+
+Include screenshots or diagrams if they help understanding.
+
+## API Reference
+
+List related API endpoints with links to API docs.
+
+### Endpoints
+
+- `METHOD /endpoint/path` - Brief description
+- `METHOD /endpoint/path` - Brief description
+
+## Configuration
+
+List any relevant configuration options (environment variables, settings).
+
+| Option | Description | Default |
+|--------|-------------|---------|
+| `VAR_NAME` | What this controls | `default_value` |
+
+## Troubleshooting
+
+### Common Issues
+
+**Issue**: Description of problem
+**Solution**: How to fix it
+
+## Related Features
+
+- [Feature Name](link.md) - How this relates
+- [Feature Name](link.md) - How this relates
+
+## See Also
+
+- [API Documentation](../api/feature.md)
+- [Architecture Documentation](../architecture/feature.md)