Pure-client port — runs entirely in the browser, no server

[cakirmert]

Hi Lukas,

I had a go at reworking the site so it can be served as plain static
files (no Flask/Dash, no Python backend, no database). Everything is in
static/; the Dash app at the repo root is untouched.

Live preview

A GitHub Actions workflow deploys the static/ folder to GitHub Pages on
every push. Live preview from my fork:

https://cakirmert.github.io/multipage_website/

When you merge, you can flip Settings → Pages → Source to "GitHub Actions"
once and your repo will deploy itself the same way.

How it works

• PHREEQC compiled to WebAssembly via Emscripten — runs in the visitor's
  browser. Numerically validated against phreeqpython to 6+ significant
  figures on pH and dissolved-carbon totals (7 reference cases pass at
  0.1 % tolerance, 3 realistic 8-input water compositions pass at 5 %).
• The seawater carbonate system uses a JS port of CO2SYS (Mehrbach 73 +
  Mucci 83 constants). Within 5 % of PyCO2SYS across 7 reference cases.
• DIC vs pCO2 ships a precomputed 51 × 61 grid for instant interactivity.
• Bjerrum, XRF, Charge balance, Forsterite, Lasaga are pure-JS
  ports of the existing math.
• Markdown narrative + LaTeX equations preserved via marked + KaTeX.

Things you'll likely want to change before going public

1. Impressum — I added a "Hosting" section mentioning Cloudflare Pages
   with DigitalOcean as alternative. Pick whichever you actually use and
   delete the other (and update wording if needed).
2. Datenschutz — same; if the actual host logs more than IP/timestamp,
   the wording may need tightening.
3. Background image / logo — copied from your existing assets/,
   no changes. Confirm they're the ones you want.
4. References / equations — markdown copied verbatim from your
   assets/*.md. If any have updated since (Rimstidt 2012, Lasaga 1994,
   Mehrbach references, etc.), the source files in
   static/assets/markdown/ are what to edit.
5. co2sys.js constants — uses Mehrbach 73 refit (PyCO2SYS
   opt_k_carbonic=4). Current PyCO2SYS default is Sulpis 2020
   (opt=16). If you want exact parity with current PyCO2SYS, the
   constant set in static/js/co2sys.js needs
   updating; I picked the older one because it's well-documented and
   gives clean closed-form pK1/pK2 expressions.

How to read this PR

• static/README.md — overview + quickstart
• static/BUILD.md — exactly how the WASM-PHREEQC
  binary was built (the build chain is gitignored to keep the diff
  reasonable; this doc is the recipe to reproduce)
• static/test/ — three Node validators that diff the
  in-browser output against direct Python runs

Why a draft PR

So you can review at your pace; happy to address feedback or split it
into smaller PRs if that's easier.