feat(image-import): add inline levenshtein distance helper

image-import.js

@@ -175,6 +175,34 @@ class ImageImporter {
 
         return { month, year, entries: validEntries, notes };
     }
+
+    /**
+     * Levenshtein distance (O(m*n) DP, inline).
+     * Inputs are expected to already be normalized.
+     * @param {string} a
+     * @param {string} b
+     * @returns {number}
+     */
+    levenshtein(a, b) {
+        if (a === b) return 0;
+        if (!a.length) return b.length;
+        if (!b.length) return a.length;
+        const m = a.length, n = b.length;
+        const dp = Array.from({ length: m + 1 }, () => new Array(n + 1).fill(0));
+        for (let i = 0; i <= m; i++) dp[i][0] = i;
+        for (let j = 0; j <= n; j++) dp[0][j] = j;
+        for (let i = 1; i <= m; i++) {
+            for (let j = 1; j <= n; j++) {
+                const cost = a[i - 1] === b[j - 1] ? 0 : 1;
+                dp[i][j] = Math.min(
+                    dp[i - 1][j] + 1,
+                    dp[i][j - 1] + 1,
+                    dp[i - 1][j - 1] + cost
+                );
+            }
+        }
+        return dp[m][n];
+    }
 }
 
 // Verbatim system prompt — German with Umlaute (per spec §7.3).