DataSourceConfig refactored to enum: External/Clock/StaticText. Clock
generates formatted time via chrono, static text emits configured string.
ESP32: connection status indicator (green/red dot bottom-right), per-widget
clear before redraw, RenderEvent enum for local + server messages.
Polling uses DataUpdate instead of ScreenUpdate to avoid wiping widget state.
Empty mappings passthrough raw source data for internal sources.
bootstrap: tracing-subscriber with RUST_LOG env filter, ServerConfig
from env vars (KFRAME_DATABASE_URL, KFRAME_TCP_ADDR, etc.), dotenvy
for .env file loading. Replaced all println with tracing macros.
tcp-server: replaced println with tracing::info/warn.
Added .env.example and .gitignore for db files.
bootstrap: SQLite config, HTTP API on :3000, TCP on :2699, poll loops.
http-api: added serve() so bootstrap doesn't depend on axum directly.
polling: reads data sources from config, polls via http-json adapter,
pushes changed widgets to connected clients.
configure via API, e.g.:
curl -X POST localhost:3000/api/data-sources -H 'Content-Type: application/json' -d '{...}'
curl -X PUT localhost:3000/api/layout -H 'Content-Type: application/json' -d '{...}'
