Claude/optimize main file size 1ak4o - #111

…S modules

The main file was a single 4,411-line file containing all frontend logic.
This splits it into focused modules under frontend/js/modules/:

- state.js (70 lines) — shared mutable state
- helpers.js (98 lines) — utility functions (rtgColor, escapeHTML, debounce, etc.)
- validation.js (238 lines) — security/input validation, URL sanitization
- analytics.js (65 lines) — click and search tracking
- tooltips.js (287 lines) — info tooltips and modal system
- search.js (604 lines) — smart search index, fuzzy matching, suggestions
- ratings.js (787 lines) — star ratings, review modal, reviews drawer, toasts
- cards.js (521 lines) — tire card rendering and lazy image loading
- favorites.js (108 lines) — user favorites system
- filters.js (1,005 lines) — filtering, sorting, pagination, URL state
- compare.js (71 lines) — compare bar logic
- server.js (210 lines) — server-side pagination mode
- image-modal.js (52 lines) — full-screen image preview

The main entry point (rivian-tires.js) is now ~408 lines, handling only
imports, event delegation wiring, and initialization. esbuild bundles
all modules into a single IIFE output — no changes to how WordPress loads
the script. All 83 existing tests continue to pass.

https://claude.ai/code/session_017rXHMqjGbMFnzGqRxxGszL