feat(clients): add nim-allographer client with BaraDB driver support

- Pure Nim wire protocol client (async + sync, no C FFI)
- Query Builder: fluent API, SQL generator, execution, transactions
- Schema Builder: create/alter/drop tables, column operations
- Connection pool with aging and timeout handling
- ORM integration via compile-time DB_BARADB switch
- Tests: test_open, test_query
- Documentation: README.md, PLAN_BARADB.md

clients/nim-allographer/example/postgres/test.c

@@ -0,0 +1,147 @@
+// gcc -I/usr/include/postgresql -I/usr/local/include/curl -o test test.c -lpq -lcurl && ./test
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <libpq-fe.h>
+#include <string.h>
+#include <curl/curl.h>
+
+struct MemoryStruct
+{
+  unsigned char *memory;
+  size_t size;
+};
+
+static size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
+{
+  size_t realsize = size * nmemb;
+  struct MemoryStruct *mem = (struct MemoryStruct *)userp;
+
+  mem->memory = realloc(mem->memory, mem->size + realsize);
+  if (mem->memory == NULL)
+  {
+    /* out of memory! */
+    printf("not enough memory (realloc returned NULL)\n");
+    return 0;
+  }
+
+  memcpy(&(mem->memory[mem->size]), contents, realsize);
+  mem->size += realsize;
+
+  return realsize;
+}
+
+void exit_nicely(PGconn *conn)
+{
+  PQfinish(conn);
+  exit(1);
+}
+
+int main()
+{
+
+  // ##################################################
+  // # Binary image
+  // ##################################################
+
+  CURL *curl_handle;
+  CURLcode curlRes;
+
+  struct MemoryStruct chunk;
+
+  chunk.memory = malloc(1); /* will be grown as needed by the realloc above */
+  chunk.size = 0;           /* no data at this point */
+
+  curl_global_init(CURL_GLOBAL_ALL);
+
+  /* init the curl session */
+  curl_handle = curl_easy_init();
+
+  /* specify URL to get */
+  curl_easy_setopt(curl_handle, CURLOPT_URL, "https://nim-lang.org/assets/img/twitter_banner.png");
+
+  /* send all data to this function  */
+  curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
+
+  /* we pass our 'chunk' struct to the callback function */
+  curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)&chunk);
+
+  /* some servers don't like requests that are made without a user-agent
+     field, so we provide one */
+  curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
+
+  /* get it! */
+  curlRes = curl_easy_perform(curl_handle);
+
+  /* check for errors */
+  if (curlRes != CURLE_OK)
+  {
+    fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(curlRes));
+  }
+  else
+  {
+    printf("%lu bytes retrieved\n", (long)chunk.size);
+  }
+
+  /* cleanup curl stuff */
+  curl_easy_cleanup(curl_handle);
+
+  /* we're done with libcurl, so clean it up */
+  curl_global_cleanup();
+
+  // ##################################################
+  // # Postgres
+  // ##################################################
+  const char *conninfo;
+  PGconn *conn;
+  PGresult *res;
+
+  // Specify your connection info
+  conninfo = "dbname=database user=user password=pass hostaddr=postgres port=5432";
+
+  // Make a connection to the database
+  // conn = PQconnectdb(conninfo);
+  conn = PQsetdbLogin("postgres", "5432", NULL, NULL, "database", "user", "pass");
+
+  // Check to see that the backend connection was successfully made
+  if (PQstatus(conn) != CONNECTION_OK)
+  {
+    fprintf(stderr, "Connection to database failed: %s", PQerrorMessage(conn));
+    exit_nicely(conn);
+  }
+
+  // Your binary data
+  // unsigned char binary_data[] = {0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x2c, 0x20, 0x57, 0x6f, 0x72, 0x6c, 0x64, 0x21};
+  unsigned char binary_data[chunk.size];
+  memcpy(binary_data, chunk.memory, chunk.size);
+  int binary_data_size = sizeof(binary_data) / sizeof(binary_data[0]);
+
+  // INSERT query
+  const char *query = "INSERT INTO image (data) VALUES ($1)";
+
+  const char *paramValues[1];
+  int paramLengths[1];
+  int paramFormats[1];
+
+  paramValues[0] = (char *)binary_data;
+  paramLengths[0] = binary_data_size;
+  paramFormats[0] = 1; // binary
+
+  // Execute the INSERT statement
+  res = PQexecParams(conn, query, 1, NULL, paramValues, paramLengths, paramFormats, 1);
+
+  if (PQresultStatus(res) != PGRES_COMMAND_OK)
+  {
+    fprintf(stderr, "INSERT command failed: %s", PQerrorMessage(conn));
+    PQclear(res);
+    exit_nicely(conn);
+  }
+
+  // Clear result
+  PQclear(res);
+
+  // Close connection
+  PQfinish(conn);
+
+  return 0;
+}