Embed webapp into the binary with fs-embed, drop --static-dir

ottyl was requiring webapp/dist to be shipped alongside the binary and
served via ServeDir/ServeFile pointed at a --static-dir CLI arg. Embed
the built webapp at compile time instead, so ottyl is a single
self-contained executable with no runtime static directory dependency.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

README.md

@@ -11,6 +11,17 @@ cli_command --verbose | ottyl
 
 ```
 
+# Building
+
+The webapp is embedded into the `ottyl` binary at compile time, so `webapp/dist` must exist *before* running `cargo build`:
+
+```bash
+cd webapp && npm install && npm run build && cd ..
+cargo build --release
+```
+
+The resulting binary is self-contained — no `webapp/dist` directory or `--static-dir` flag is needed at runtime.
+
 # Architecture
 
 ottyl reads the logs via stdin and indexes it in-memory in a BTreeMap for property search.