docs(mcp): fix python -m invocation in README — point at .server module

Addresses Copilot's suppressed-confidence comment on PR #166 (which the
reviewer surfaced manually): the \"Using Python Environment\" example
told users to invoke \`python -m stocktrim_mcp_server\`, but the package
ships no \`__main__.py\` so that command fails at runtime with:

    /path/python: No module named stocktrim_mcp_server.__main__;
    'stocktrim_mcp_server' is a package and cannot be directly executed

Users following the example would hit this immediately.

Fix: change the example's args to \`[\"-m\", \"stocktrim_mcp_server.server\"]\`
— \`server.py\` already exposes \`main()\` and an \`if __name__ == \"__main__\"\`
guard, so it's directly runnable today. Smoke-tested:
\`uv run python -m stocktrim_mcp_server.server\` launches the FastMCP
server end-to-end (prompts registered, caching enabled, server starting).

Considered adding a \`__main__.py\` shim to make the original short form
work — rejected because that would expand the public invocation surface
beyond what the existing console script (\`stocktrim-mcp-server\`) and the
\`.mcpb\` bundle already cover. Pointing at the module that already exists
is the minimum correct change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dougborg

stocktrim_mcp_server/README.md

@@ -116,7 +116,7 @@ If you have the server installed in a specific Python environment:
   "mcpServers": {
     "stocktrim": {
       "command": "python",
-      "args": ["-m", "stocktrim_mcp_server"],
+      "args": ["-m", "stocktrim_mcp_server.server"],
       "env": {
         "STOCKTRIM_API_AUTH_ID": "your_tenant_id_here",
         "STOCKTRIM_API_AUTH_SIGNATURE": "your_tenant_name_here"