Move blockchain app READMEs to centralized documentation

- Relocate blockchain-event-bridge README content to docs/apps/blockchain/blockchain-event-bridge.md
- Relocate blockchain-explorer README content to docs/apps/blockchain/blockchain-explorer.md
- Replace app READMEs with redirect notices pointing to new documentation location
- Consolidate documentation in central docs/ directory for better organization

docs/apps/plugins/plugin-marketplace.md

@@ -0,0 +1,223 @@
+# Plugin Marketplace
+
+## Status
+✅ Operational
+
+## Overview
+Marketplace plugin for discovering, installing, and managing AITBC plugins and extensions.
+
+## Architecture
+
+### Core Components
+- **Plugin Catalog**: Catalog of available plugins
+- **Plugin Installer**: Handles plugin installation and updates
+- **Dependency Manager**: Manages plugin dependencies
+- **Version Manager**: Handles plugin versioning
+- **License Manager**: Manages plugin licenses
+
+## Quick Start (End Users)
+
+### Prerequisites
+- Python 3.13+
+- Internet access for plugin downloads
+- Sufficient disk space for plugins
+
+### Installation
+```bash
+cd /opt/aitbc/apps/plugin-marketplace
+.venv/bin/pip install -r requirements.txt
+```
+
+### Configuration
+Set environment variables in `.env`:
+```bash
+PLUGIN_REGISTRY_URL=https://plugins.aitbc.com
+INSTALLATION_PATH=/opt/aitbc/plugins
+AUTO_UPDATE_ENABLED=false
+```
+
+### Running the Service
+```bash
+.venv/bin/python main.py
+```
+
+## Developer Guide
+
+### Development Setup
+1. Clone the repository
+2. Create virtual environment: `python -m venv .venv`
+3. Install dependencies: `pip install -r requirements.txt`
+4. Configure plugin registry
+5. Run tests: `pytest tests/`
+
+### Project Structure
+```
+plugin-marketplace/
+├── src/
+│   ├── plugin_catalog/       # Plugin catalog
+│   ├── plugin_installer/    # Plugin installation
+│   ├── dependency_manager/  # Dependency management
+│   ├── version_manager/      # Version management
+│   └── license_manager/     # License management
+├── tests/                   # Test suite
+└── pyproject.toml           # Project configuration
+```
+
+### Testing
+```bash
+# Run all tests
+pytest tests/
+
+# Run installer tests
+pytest tests/test_installer.py
+
+# Run dependency manager tests
+pytest tests/test_dependencies.py
+```
+
+## API Reference
+
+### Plugin Catalog
+
+#### List Plugins
+```http
+GET /api/v1/marketplace/plugins?category=analytics&limit=20
+```
+
+#### Get Plugin Details
+```http
+GET /api/v1/marketplace/plugins/{plugin_id}
+```
+
+#### Search Plugins
+```http
+POST /api/v1/marketplace/plugins/search
+Content-Type: application/json
+
+{
+  "query": "analytics",
+  "filters": {
+    "category": "string",
+    "version": "string"
+  }
+}
+```
+
+### Plugin Installation
+
+#### Install Plugin
+```http
+POST /api/v1/marketplace/plugins/install
+Content-Type: application/json
+
+{
+  "plugin_id": "string",
+  "version": "string",
+  "auto_dependencies": true
+}
+```
+
+#### Uninstall Plugin
+```http
+DELETE /api/v1/marketplace/plugins/{plugin_id}
+```
+
+#### Update Plugin
+```http
+POST /api/v1/marketplace/plugins/{plugin_id}/update
+Content-Type: application/json
+
+{
+  "version": "string"
+}
+```
+
+#### Get Installation Status
+```http
+GET /api/v1/marketplace/plugins/{plugin_id}/status
+```
+
+### Dependencies
+
+#### Get Plugin Dependencies
+```http
+GET /api/v1/marketplace/plugins/{plugin_id}/dependencies
+```
+
+#### Resolve Dependencies
+```http
+POST /api/v1/marketplace/dependencies/resolve
+Content-Type: application/json
+
+{
+  "plugin_ids": ["plugin1", "plugin2"]
+}
+```
+
+### Versions
+
+#### List Plugin Versions
+```http
+GET /api/v1/marketplace/plugins/{plugin_id}/versions
+```
+
+#### Get Version Compatibility
+```http
+GET /api/v1/marketplace/plugins/{plugin_id}/compatibility?version=1.0.0
+```
+
+### Licenses
+
+#### Validate License
+```http
+POST /api/v1/marketplace/licenses/validate
+Content-Type: application/json
+
+{
+  "plugin_id": "string",
+  "license_key": "string"
+}
+```
+
+#### Get License Info
+```http
+GET /api/v1/marketplace/plugins/{plugin_id}/license
+```
+
+## Configuration
+
+### Environment Variables
+- `PLUGIN_REGISTRY_URL`: URL for plugin registry
+- `INSTALLATION_PATH`: Path for plugin installation
+- `AUTO_UPDATE_ENABLED`: Enable automatic plugin updates
+- `MAX_CONCURRENT_INSTALLS`: Maximum concurrent installations
+
+### Plugin Categories
+- **Analytics**: Data analysis and reporting plugins
+- **Security**: Security scanning and monitoring plugins
+- **Infrastructure**: Infrastructure management plugins
+- **Trading**: Trading and exchange plugins
+
+### Installation Parameters
+- **Installation Path**: Directory for plugin installation
+- **Dependency Resolution**: Automatic dependency handling
+- **Version Constraints**: Version compatibility checks
+
+## Troubleshooting
+
+**Plugin installation failed**: Check plugin compatibility and dependencies.
+
+**License validation failed**: Verify license key and plugin ID.
+
+**Dependency resolution failed**: Check dependency conflicts and versions.
+
+**Auto-update not working**: Verify auto-update configuration and registry connectivity.
+
+## Security Notes
+
+- Validate plugin signatures before installation
+- Scan plugins for security vulnerabilities
+- Use HTTPS for plugin downloads
+- Implement plugin sandboxing
+- Regularly update plugins for security patches
+- Monitor for malicious plugin behavior