Add streaming brotli compression and hot-reloadable config (livevue.toml)

Key changes:

- **src/config.rs** – `LiveVueConfig` (server host/port, brotli quality +
  window size), loaded from `livevue.toml`. A notify-based file watcher
  reloads the config on any file change; a SIGHUP handler does the same on
  demand. Falls back to compiled-in defaults when the file is absent.

- **src/brotli_layer.rs** – `BrotliBody`, a custom `http_body::Body` wrapper
  that streams brotli-compressed data through a single persistent
  `brotli::CompressorWriter`. The encoder survives across SSE event flushes,
  so its sliding window accumulates context from all prior events —
  progressively better compression as the stream grows. Both quality (0–11)
  and window size (lgwin 10–24, i.e. 1 KB – 16 MB) are taken from config.
  `brotli_compression` is an axum `from_fn_with_state` middleware that
  activates only when the client sends `Accept-Encoding: br`.

- **src/server.rs** – `AppState` gains a `config: SharedConfig` field.
  `AppState::new` takes the config; `AppState::new_default` is a zero-config
  convenience constructor.

- **livevue.toml** – documented example config with inline comments
  explaining each field and the brotli window-size tradeoff table.

- **examples/todo** – loads config via `load_and_watch_config`, derives the
  bind address from `config.server`, and applies `brotli_compression` as a
  router layer.

https://claude.ai/code/session_01UnQQkkwts64FPUsSzFfdQb

src/lib.rs

@@ -5,6 +5,8 @@ pub mod context;
 pub mod connection;
 pub mod sse;
 pub mod server;
+pub mod config;
+pub mod brotli_layer;
 
 /// PostgreSQL logical replication module.
 ///
@@ -30,4 +32,6 @@ pub use pg_query::PgQuery;
 pub use context::{RenderContext, ComponentTree, ComponentNode};
 pub use connection::{ConnectionManager, ConnectionState, SubscriptionRegistry};
 pub use sse::{format_patch_elements, format_patch_signals};
-pub use server::{AppState, SharedState, RenderFn, sse_handler, spawn_fanout, ingest_signals, ActionParams, SseParams};
+pub use server::{AppState, SharedState, RenderFn, sse_handler, spawn_fanout, ingest_signals, ActionParams, SseParams};
+pub use config::{LiveVueConfig, ServerConfig, BrotliConfig, SharedConfig, load_config, load_and_watch_config};
+pub use brotli_layer::brotli_compression;