feat: initial scaffold of kanban_cpp v2 (issue 0130)

Frontend C++ ImGui (main.cpp + 4 paneles) + backend Go (HTTP + SQLite + fsnotify + SSE).
Reusa parse/scan/watch funcs del registry (issue 0130a).

main.cpp

@@ -0,0 +1,107 @@
+#include <imgui.h>
+#include <atomic>
+#include <chrono>
+#include <cstdio>
+#include <cstring>
+#include <string>
+#include <thread>
+
+#include "app_base.h"
+#include "core/panel_menu.h"
+#include "core/icons_tabler.h"
+#include "core/logger.h"
+
+#include "panels.h"
+#include "data.h"
+
+static bool g_show_board   = true;
+static bool g_show_flows   = true;
+static bool g_show_filters = true;
+static bool g_show_detail  = true;
+
+static std::atomic<bool> g_refresh_thread_alive{false};
+static std::thread       g_refresh_thread;
+
+static void start_refresh_thread() {
+    g_refresh_thread_alive = true;
+    g_refresh_thread = std::thread([]() {
+        kanban::refresh_meta();
+        kanban::refresh_issues();
+        kanban::refresh_flows();
+        kanban::start_sse();
+        while (g_refresh_thread_alive) {
+            std::this_thread::sleep_for(std::chrono::seconds(30));
+            if (!g_refresh_thread_alive) break;
+            kanban::refresh_issues();
+            kanban::refresh_flows();
+        }
+        kanban::stop_sse();
+    });
+}
+
+static void stop_refresh_thread() {
+    g_refresh_thread_alive = false;
+    if (g_refresh_thread.joinable()) g_refresh_thread.join();
+}
+
+static void render() {
+    if (g_show_board)   kanban::draw_board();
+    if (g_show_flows)   kanban::draw_flows();
+    if (g_show_filters) kanban::draw_filters();
+    if (g_show_detail)  kanban::draw_detail();
+}
+
+static int run_self_test() {
+    kanban::State& s = kanban::state();
+    s.backend_url = "http://127.0.0.1:1";
+    bool ok_issues = kanban::refresh_issues();
+    bool ok_flows  = kanban::refresh_flows();
+    if (ok_issues || ok_flows) {
+        std::fprintf(stderr, "[self-test] expected refresh to fail on unreachable backend\n");
+        return 1;
+    }
+    kanban::Issue dummy;
+    dummy.status = "pendiente";
+    dummy.priority = "media";
+    if (!kanban::passes_filters(dummy)) {
+        std::fprintf(stderr, "[self-test] empty filters should let issue pass\n");
+        return 2;
+    }
+    s.filters.priorities.insert("alta");
+    if (kanban::passes_filters(dummy)) {
+        std::fprintf(stderr, "[self-test] priority filter should reject media when alta required\n");
+        return 3;
+    }
+    std::fprintf(stdout, "[self-test] ok\n");
+    return 0;
+}
+
+int main(int argc, char** argv) {
+    for (int i = 1; i < argc; ++i) {
+        if (std::strcmp(argv[i], "--self-test") == 0) {
+            return run_self_test();
+        }
+        if (std::strcmp(argv[i], "--backend") == 0 && i + 1 < argc) {
+            kanban::state().backend_url = argv[++i];
+        }
+    }
+
+    static fn_ui::PanelToggle panels[] = {
+        { "Board",   nullptr, &g_show_board   },
+        { "Flows",   nullptr, &g_show_flows   },
+        { "Filters", nullptr, &g_show_filters },
+        { "Detail",  nullptr, &g_show_detail  },
+    };
+
+    fn::AppConfig cfg;
+    cfg.title       = "kanban_cpp v2 — dev/issues + dev/flows";
+    cfg.about       = { "kanban_cpp", "0.2.0", "Kanban C++ v2 — gestor de dev/issues y dev/flows del registry" };
+    cfg.log         = { "kanban_cpp.log", 1 };
+    cfg.panels      = panels;
+    cfg.panel_count = sizeof(panels) / sizeof(panels[0]);
+
+    start_refresh_thread();
+    int rc = fn::run_app(cfg, render);
+    stop_refresh_thread();
+    return rc;
+}