feature: add --transport CLI flag (stdio/sse/streamable-http) for containerized deployments

Context

paper_search_mcp/server.py:main() calls mcp.run(transport="stdio") unconditionally. Works cleanly for stdio subprocess consumers (Claude Desktop, Cursor, Claude Code skill).

Problem

Consumers that run the MCP as a networked service cannot use it directly:

• Container deployments behind HTTP/SSE MCP gateways (agentgateway, Docker MCP gateway's HTTP route, ToolHive)
• Kubernetes deployments where the backend is reached via a Service, not a forked subprocess
• Remote MCP scenarios where the MCP lifecycle isn't owned by the client

The current workaround is an extra container running sparfenyuk/mcp-proxy to bridge stdio↔HTTP.

Proposal

Add CLI args to main(), preserving stdio as default. Sketch:

import argparse
from mcp.server.fastmcp import FastMCP
# ... existing imports ...

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--transport", choices=["stdio", "sse", "streamable-http"], default="stdio")
    parser.add_argument("--host", default="127.0.0.1")
    parser.add_argument("--port", type=int, default=8000)
    parser.add_argument("--path", default="/mcp")
    args = parser.parse_args()

    # host/port/path are init-time settings on FastMCP v1.x (mcp>=1.8.0)
    mcp = FastMCP(
        "paper_search_server",
        host=args.host,
        port=args.port,
        streamable_http_path=args.path,
    )
    # ... existing tool registrations ...
    mcp.run(transport=args.transport)

Requires bumping the mcp[cli] floor from >=1.6.0 to >=1.8.0 (streamable-http transport landed in v1.8.0).

Precedent

--transport {stdio,sse,streamable-http} is the emerging convention for multi-transport MCP servers — used by FastMCP's own CLI (fastmcp run --transport ...), Grafana, Notion, and mcp-atlassian, plus client-side in Claude Code (claude mcp add --transport ...), Gemini CLI, and ToolHive. Not universal (many servers remain stdio-only), but the clearest shared shape.

Backward compatibility

• Default stays stdio — existing Claude Desktop / skill users see no change
• Purely additive, same shape as Add CLI entry point for uvx compatibility #16 uvx CLI entry point

Happy to submit a PR if this would be accepted.