Add ArXiv MCP Server for academic research and paper analysis (#66)

* Add ArXiv MCP Server for academic research and paper analysis

Features:
• Search arXiv papers with advanced filtering (date, category, query)
• Download and store papers locally as markdown
• Read and analyze paper content programmatically
• Deep research analysis prompts for comprehensive paper review
• Configurable local storage path for paper management

Technical Details:
- Category: search (academic research focused)
- License: Apache 2.0 (compatible with Docker registry)
- Source: https://github.com/jasonleinart/arxiv-mcp-server
- Build Status: Successfully tested and validated
- Docker Image: mcp/arxiv-mcp-server

Target Users:
Perfect for researchers, academics, and AI assistants conducting
literature reviews, research analysis, and academic paper exploration.

Differentiates from existing paper-search server by providing:
- ArXiv-specific optimizations and direct API integration
- Local paper storage and management capabilities
- Research-focused analysis prompts and workflows
- Advanced filtering and categorization options

* FIX: Add proper volume mounting to ArXiv MCP server

- Maps user storage path to /app/papers inside container
- Enables file persistence for downloaded papers
- Fixes ephemeral container issue where files weren't saved
- Follows pattern used by kubectl-mcp-server and elevenlabs
- Essential for Docker MCP Toolkit volume mounting

* FIX: Use environment variable for volume mounting

- Change from parameter template to environment variable approach
- Docker MCP Toolkit processes  but not {{parameter}} templates
- Maps storage_path parameter to STORAGE_PATH env var for volume mounting
- Should resolve volume mounting issue where files weren't persisting

* FIX: Correct volume mounting configuration per PR feedback

- Change volume mapping from $STORAGE_PATH to {{arxiv-mcp-server.storage_path}} template syntax
- Add ARXIV_STORAGE_PATH environment variable for internal container path
- Fixes volume mounting issue identified by @cmrigney in PR review
- Follows Docker MCP Registry configuration standards per docs/configuration.md

* FIX: Apply reviewer's suggestion - Use only ARXIV_STORAGE_PATH environment variable

- Remove redundant STORAGE_PATH environment variable as suggested by @cmrigney
- Keep only ARXIV_STORAGE_PATH with '/app/papers' value for container internal path
- Simplifies configuration while maintaining full functionality
- Volume mounting handles path mapping: {{arxiv-mcp-server.storage_path}}:/app/papers
- ArXiv server auto-detects Docker environment and uses correct storage path

Author: jasonleinart

servers/arxiv-mcp-server/server.yaml

@@ -0,0 +1,46 @@
+name: arxiv-mcp-server
+image: mcp/arxiv-mcp-server
+type: server
+meta:
+  category: search
+  tags:
+    - arxiv
+    - research
+    - academic
+    - papers
+    - search
+    - ai
+about:
+  title: ArXiv MCP Server
+  description: |
+    The ArXiv MCP Server provides a comprehensive bridge between AI assistants and arXiv's research repository through the Model Context Protocol (MCP). 
+    
+    Features:
+    • Search arXiv papers with advanced filtering
+    • Download and store papers locally as markdown
+    • Read and analyze paper content
+    • Deep research analysis prompts
+    • Local paper management and storage
+    
+    Perfect for researchers, academics, and AI assistants conducting literature reviews and research analysis.
+  icon: https://avatars.githubusercontent.com/u/15390319?v=4
+source:
+  project: https://github.com/jasonleinart/arxiv-mcp-server
+run:
+  volumes:
+    - '{{arxiv-mcp-server.storage_path}}:/app/papers'
+config:
+  description: Configure local storage path for downloaded papers
+  env:
+    - name: ARXIV_STORAGE_PATH
+      example: /Users/local-test/papers
+      value: '/app/papers'
+  parameters:
+    type: object
+    properties:
+      storage_path:
+        type: string
+        description: Directory path where downloaded papers will be stored
+        default: /Users/local-test/papers
+    required:
+      - storage_path