feat: text normalization with medical abbreviation expansion

src/normalize.rs

@@ -1 +1,23 @@
-// implemented in a later task
+/// (pattern, replacement) — applied as whole-token, case-insensitive.
+const ABBREV: &[(&str, &str)] = &[
+    ("v.a.", "verdacht auf"),
+    ("z.n.", "zustand nach"),
+    ("art.", "arterielle"),
+    ("op", "operation"),
+    ("dd", "differentialdiagnose"),
+    ("re.", "rechts"),
+    ("li.", "links"),
+];
+
+pub fn normalize(input: &str) -> String {
+    let lower = input.to_lowercase();
+    let mut out: Vec<String> = Vec::new();
+    for tok in lower.split_whitespace() {
+        let replaced = ABBREV.iter()
+            .find(|(p, _)| *p == tok)
+            .map(|(_, r)| r.to_string())
+            .unwrap_or_else(|| tok.to_string());
+        out.push(replaced);
+    }
+    out.join(" ")
+}