feat: add Lume.js framework implementation

[sathvikc]

Summary

• Adds a complete Lume.js implementation of the weather app (apps/lume-js/)
• Loads Lume.js v2.1.0 from CDN — no build step required (same philosophy as Alpine.js)
• Uses state(), bindDom(), computed(), repeat(), and the show handler from the Lume.js API
• All 22 Playwright tests pass against the CDN build
• Added Lume.js entry to frameworks.json with logo, description, and links
• Added dark mode support to assets/styles/design-system.css (canonical shared CSS)
• Updated .github/README.md: logo grid, community stats table, and CI status table

About Lume.js

Lume.js is a lightweight reactive library (~5.58 KB full gzipped) with no build step. It is HTML-first like Alpine.js but uses a flat reactive store model (state() + bindDom()) rather than inline directives — making it closer to vanilla JS in mental model.

Bundle: Single <script defer> tag from jsDelivr CDN — no npm install, no Vite, no bundler.

<script defer src="https://cdn.jsdelivr.net/npm/lume-js@2.1.0/dist/lume.global.js"></script>

const { state, bindDom, computed, repeat, show } = window.Lume;

Test plan

• 22/22 Playwright E2E tests passing locally
• npm run lint:lume-js passes (ESLint flat config, zero errors)
• CDN URL resolves (HTTP 200, lume-js@2.1.0 on jsDelivr)
• Dark mode renders correctly via shared CSS variable overrides
• App loads and functions: search, current weather, 7-day forecast, localStorage persistence