Document config vars and rewrite README

- Clarified HERMES_API_KEY and PRICE_PER_VERSION comments in config.py.
- Completely rewrote README.md with:
  - version, overview, and table of contents
  - page-by-page customer and admin guide
  - status flow table
  - detailed /admin/settings section
  - Docker / Portainer install process
  - full environment variable table
  - local development and troubleshooting sections

config.py

@@ -79,8 +79,9 @@ class Config:
     # Default customer revision limit if not overridden in runtime settings.
     MAX_REVISIONS = int(os.environ.get('MAX_REVISIONS', '2'))
 
-    # API key used by Hermes to POST generated Suno prompts back to the website.
-    # Also stored (encrypted) in runtime settings so it can be regenerated from /admin/settings.
+    # API key used by Hermes / an AI assistant to POST generated Suno prompts
+    # back to /api/prompt/<id>. If provided via env var it overrides the value
+    # stored in runtime settings. Stored encrypted when set from /admin/settings.
     HERMES_API_KEY = os.environ.get('HERMES_API_KEY', '')
 
     # Booth name used in customer-facing text and email sign-offs.
@@ -89,7 +90,8 @@ class Config:
     # Internal port gunicorn listens on inside the container (also exposed in Dockerfile).
     INTERNAL_PORT = int(os.environ.get('INTERNAL_PORT', '8000'))
 
-    # Informational price shown to the operator/customer; actual payment is collected manually (e.g. Square).
+    # Legacy single-price label. Current pricing is configured per-item from
+    # /admin/pricing, but this value is still displayed in a few templates.
     PRICE_PER_VERSION = float(os.environ.get('PRICE_PER_VERSION', '10.00'))
     CURRENCY = os.environ.get('CURRENCY', 'CAD')