refactor: take the frontend apart into modules

The 2,800-line app.js becomes twenty-one modules under frontend/src — dom,
constants, state, engine, events, catalog, session, navigation, overview,
grid, legend, pins, zones, search, detail, styles, theme, util, boot, and
diagnostics — with app.js reduced to the entry that wires the stylesheet,
the parity tour, and start(). The 1,500-line stylesheet becomes thirty-one
component files under frontend/css, imported in the original order; the
built assets/app.css is byte-identical before and after. Every function
body moved verbatim: the parity tour reports the decomposed build identical
to the monolith baseline across all thirty-two steps, and the Go tests and
vet stay green. This is the ground the new visual identity gets built on -
the theme and styles modules now hold every color the JavaScript paints
with, beside a stylesheet split that gives the redesign one file per
component.

commit

2fb0bfa68a89bb8de39e0c78cb8d3fb154ef4c3a

parent

67680430ac7b76123db65bf2f4fbbfb9e07e6da1

author

Dami <dami.etoile@gmail.com>