Rename plugin to "Local REST API with MCP"

The Obsidian plugin directory rejected the previous name "Local REST API &
MCP Server" as non-compliant with naming guidelines and hid the plugin
pending a fix. The '&' character is not permitted per the Obsidian manifest
name rules.

Renamed to "Local REST API with MCP" across manifest.json, README.md,
src/constants.ts, src/main.ts, the OpenAPI description source, and the
regenerated docs/openapi.yaml.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>