fix(weather): validate coordinates at API boundaries

[rissrice2105-agent]

Summary

• parse REST latitude and longitude strictly so partial values such as 40abc are rejected
• reject non-finite and out-of-range coordinates before weather services are called
• apply the same validation to the MCP weather tool endpoint
• add focused REST, MCP, and utility regression coverage

Tests

• pnpm --dir mcp_modules/weather test (32 passing)
• targeted ESLint for Weather controller, utilities, and tests
• git diff --check

The root suite reaches 53 passing and 5 pending tests; two existing Module Loader assertions fail in the Windows environment and are unrelated to Weather.