feat: add dark mode, telemetry, and curl to Docker image

- Install `curl` in Dockerfile for healthcheck/tooling support
- Add class-based dark mode via Tailwind `@custom-variant` and a
  pre-paint `<script>` in `app.html` to avoid theme flash on load
- Implement theme toggle in layout with system preference detection,
  `localStorage` persistence, and smooth transitions
- Update all UI components with `dark:` variants for full dark mode
  support across backgrounds, borders, and text colours
- Add `sendTelemetry` helper in `api.ts` for fire-and-forget
  client-side error reporting to `/api/v1/telemetry`

.env.example

@@ -0,0 +1,30 @@
+# Nike — Football Data Platform
+# Copy to .env and fill in your values. Never commit .env.
+
+# ── TheSportsDB ──────────────────────────────────────────
+# Free test key is '3' (limited). Get a premium key at https://www.patreon.com/thesportsdb
+NIKE_SPORTSDB_KEY=3
+
+# ── Database ──────────────────────────────────────────────
+NIKE_DB_HOST=localhost
+NIKE_DB_PORT=5432
+NIKE_DB_USER=nike
+NIKE_DB_PASSWORD=
+NIKE_DB_NAME=nike
+
+# ── Server ────────────────────────────────────────────────
+NIKE_HOST=0.0.0.0
+NIKE_PORT=8000
+NIKE_LOG_LEVEL=WARNING
+
+# IPs allowed to set X-Forwarded-* headers (your HAProxy host).
+# '*' is safe when Nike's port is firewalled to HAProxy only.
+NIKE_TRUSTED_PROXY=*
+
+# ── Followed teams ────────────────────────────────────────
+# Comma-separated list of "Team Name:League Name" pairs.
+NIKE_TEAMS=Toronto FC:MLS, Arsenal:Premier League
+
+# ── Legacy (not active) ───────────────────────────────────
+# NIKE_RAPIDAPI_KEY=
+# NIKE_API_FOOTBALL_KEY=