migrate from Pico CSS to Tailwind CSS v4

Replace Pico CSS CDN with Tailwind v4 standalone CLI (no Node.js).
Brand theme with navy/electric/accent palette, component classes,
self-hosted Commit Mono font. Docker multi-stage CSS build.
Logo links to dashboard when logged in.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,20 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Changed
+- **Pico CSS → Tailwind CSS v4** — full design system migration across all templates (except planner, which keeps its own CSS)
+  - Standalone Tailwind CLI binary (no Node.js) with `make css-build` / `make css-watch`
+  - Court Tech brand theme: navy/charcoal/electric/accent color palette
+  - Component classes (`.btn`, `.card`, `.form-input`, `.table`, `.badge`, `.flash`, etc.) in `input.css` for consistent styling
+  - Self-hosted Commit Mono font (replaces JetBrains Mono) for monospace data display
+  - Docker multi-stage build: CSS compiled in dedicated stage before Python build
+- Landing page teaser calculator restyled with Tailwind utilities and brand colors
+
+### Removed
+- Pico CSS CDN dependency
+- `custom.css` (replaced by Tailwind `input.css` with `@layer components`)
+- JetBrains Mono font (replaced by self-hosted Commit Mono)
+
 ### Fixed
 - Empty env vars (e.g. `SECRET_KEY=`) now fall back to defaults instead of silently using `""` — fixes 500 on every request when `.env` has blank values