refactor: restructure core module into domain-driven packages with 2672 insertions and 2220 deletions

Splits monolithic core module into bounded contexts: identity, billing, and notification domains. Moves entity definitions, repository interfaces, and service implementations into separate packages. Updates import paths across 25 files to align with new package structure. Removes cross-domain coupling by extracting shared value objects into a common package.

.backup.1.rautocomplete.h

@@ -0,0 +1,63 @@
+#ifndef RAUTOCOMPLETE_H
+#define RAUTOCOMPLETE_H
+#define R4_DEBUG
+#include "rrex4.h"
+#include "rstring_list.h"
+#define rautocomplete_new rstring_list_new
+#define rautocomplete_free rstring_list_free
+#define rautocomplete_add rstring_list_add
+#define rautocomplete_find rstring_list_find
+#define rautocomplete_t rstring_list_t
+#define rautocomplete_contains rstring_list_contains
+
+char *r4_escape(char *content) {
+    size_t size = strlen(content) * 2 + 1;
+    char *escaped = (char *)calloc(size, sizeof(char));
+    char *espr = escaped;
+    char *to_escape = "?*+()[]{}^$\\";
+    *espr = '(';
+    espr++;
+    while (*content) {
+        if (strchr(to_escape, *content)) {
+            *espr = '\\';
+            espr++;
+        }
+        *espr = *content;
+        espr++;
+        content++;
+    }
+    *espr = '.';
+    espr++;
+    *espr = '+';
+    espr++;
+    *espr = ')';
+    espr++;
+    *espr = 0;
+    return escaped;
+}
+
+char *rautocomplete_find(rstring_list_t *list, char *expr) {
+    if (!list->count)
+        return NULL;
+    if (!expr || !strlen(expr))
+        return NULL;
+
+    char *escaped = r4_escape(expr);
+
+    for (unsigned int i = list->count - 1; i == 0; i--) {
+        char *match;
+        r4_t *r = r4(list->strings[i], escaped);
+        if (r->valid && r->match_count == 1) {
+            match = strdup(r->matches[0]);
+        }
+        r4_free(r);
+        if (match) {
+
+            free(escaped);
+            return match;
+        }
+    }
+    free(escaped);
+    return NULL;
+}
+#endif