RFC: Integrate portless for simplified HTTPS setup and remote access

[Sands-45]

The Problem

Currently, setting up the Local REST API requires users to:

1. Manually configure a port number
2. Deal with CORS issues when accessing from browsers or other apps
3. Use workarounds (self-signed certs, reverse proxies) to get HTTPS working
4. Access the API via http://localhost:, which is blocked on many browsers for security reasons and doesn't work over a network

This creates friction, especially for less technical users and for use cases like accessing the API from a phone, another device, or remotely.

The Proposal

Integrate portless to replace the current port-based setup with named, HTTPS-enabled localhost URLs.
Before:

http://localhost:27123

After:

https://obsidian.localhost

Benefits

• HTTPS out of the box - portless generates a local CA and provisions certs automatically, eliminating self-signed cert warnings
• Named URLs - https://obsidian.localhost is more memorable and intuitive than http://localhost:27123
• Simplified docs - no more explaining port selection, CORS, or HTTPS workarounds
• Remote access - via built-in Tailscale (obsidian.local) or ngrok integration, users could access their vault API from anywhere
• LAN access - other devices on the same network could reach the API at https://obsidian.local with no extra config
• Works with existing clients - the API surface stays the same, only the transport layer changes