feat: add support for single volume (/config) or dual volume (/config, /assets) setups

[vishalkadam47]

Support Flexible Asset Path Resolution for Local and Docker Environments

Allow users to organize their Glance files in two ways:

1. Simple: All files in one /config directory
2. Advanced: Split between /config (settings) and /assets (static files) - Existing setup

Changes:

• Improve path detection and validation
• Keep compatibility with existing setups
• Add helpful error messages

Single Volume Setup

Docker Compose

services:
  glance:
    image: glanceapp/glance
    volumes:
      - ./config:/app/config # All files in config directory
    ports:
      - 8080:8080

glance.yml

server:
assets-path: config
theme:
custom-css-file: /config/user.css
branding:
favicon-url: /config/favicon.png
logo-url: /config/logo.png

[vaaleyard]

This is great