Add gazetteer configuration and dependency

This commit introduces the `VOCAB_DIR` configuration option, which
specifies the directory for gazetteer files. It also adds the `strsim`
crate, which is used for calculating string similarity and is essential
for the gazetteer's functionality.

The gazetteer module has been significantly expanded to include the
`Gazetteer` struct, its loading mechanism from `.txt` files, and an
annotation function. This functionality allows for pre-LLM correction of
proper names and technical vocabulary by identifying potential
misspellings based on phonetic similarity and edit distance.

server/Cargo.toml

@@ -26,6 +26,7 @@ time = { version = "0.3.47", features = ["local-offset", "parsing", "formatting"
 toml_edit = "0.25.11"
 rpassword = "7.4.0"
 pulldown-cmark = { version = "0.13", default-features = false, features = ["html"] }
+strsim = "0.11"
 
 [dev-dependencies]
 tower = { version = "0.5", features = ["util"] }