refactor: restructure template around a shared data/types layer, hard…

[nasroykh]

…en SEO/a11y/security, and modernize tooling

Implements the AUDIT.md roadmap end-to-end. Verified: tsc, eslint (0 problems), vitest (16 passing), clean next build (SSG), and a runtime smoke test of all routes.

Architecture & data

• Add single source of truth: data/{products,categories}.ts validated by zod schemas (lib/schemas); domain types derived via z.infer and exported from @/types. Remove all inline/duplicated catalog data.
• Add async data-access layer (lib/data/products.ts) + derived search index.
• Model prices as integer cents; format at the edge with lib/format.ts. Standardize product/cart ids on string.
• Centralize brand/SEO/nav in lib/config/site.ts; validate env in lib/env.ts (siteUrl). Unify brand on 'Fashion Oasis' (was 3 spellings).

Components & RSC

• Extract ProductCard (client island) + ProductGrid (server); sections are now Server Components using CSS animations (motion only on the 404).
• Real category filtering on /men, /women, /accessories, /sale (drop the dead CategoryPage template).
• Move add-to-cart to a real sibling (no nested interactive).
• Split Footer newsletter into a client leaf; add mobile nav, theme toggle, validated contact form (react-hook-form + zod).
• Rewrite cart store: numeric subtotal/line totals, quantity clamping, pure addToCart action; fix hydration-safe rendering.

SEO / a11y / theming

• Per-page metadata + canonical/OG via lib/seo.ts; Product + BreadcrumbList JSON-LD; generateStaticParams + dynamicParams=false (true 404s); product routes in sitemap.
• Wire dark mode (next-themes + ThemeProvider + toggle), fix @custom-variant.
• Skip link, prefers-reduced-motion, cart aria labels, success/warning/rating tokens, local SVG placeholder art (drop placehold.co dependency).

Tooling, infra & docs

• Remove 7 unused deps + 7 dead ui/ files; consolidate hooks into lib/hooks.
• next.config: security headers, poweredByHeader:false, image formats, optimizePackageImports; tsconfig ES2022 + stricter flags; Prettier, EditorConfig, .nvmrc, engines/packageManager, CI workflow.
• Dockerfile: Node 24, drop dead deps stage, fix HEALTHCHECK to /api/health (+ real health route); fix compose/Makefile/validate-script.
• Vitest unit tests; fix ESLint 10 + eslint-plugin-react crash.
• Sweep docs (README/LLMS/CLAUDE/DOCKER): correct versions, remove the non-existent 'Radix UI', document build-time env semantics. Add AUDIT.md, LICENSE, CONTRIBUTING.