feat: full feature set - filters, context menu, patchbay, position persistence

Backend:
- GET/PUT /api/positions - server-side node position persistence (~/.config/pwweb/)
- GET/PUT /api/patchbay - save/load connection snapshots
- POST /api/patchbay/apply - apply saved connections

Frontend (custom SVG canvas):
- Right-click wire to disconnect (context menu)
- Port type filter toolbar (audio/midi/video/other toggles)
- Save/Load patchbay buttons
- Node positions persisted to localStorage + server
- Node border color by mode (green=output, red=input)
- Type indicator in node header [audio] [midi]
- Selected wire highlight (white, thicker)
- Select wire + Delete to disconnect
- Drag output port to input port to connect
- Pan (drag bg) and zoom (scroll wheel)
- Filtered ports shown as dim dots when hidden

src/web_server.cpp

@@ -4,9 +4,40 @@
 #include <cstdio>
 #include <algorithm>
 #include <condition_variable>
+#include <fstream>
+#include <sys/stat.h>
+#include <pwd.h>
 
 using namespace pwgraph;
 
+// ============================================================================
+// File I/O helpers
+// ============================================================================
+
+std::string WebServer::dataDir() const {
+    const char *home = getenv("HOME");
+    if (!home) {
+        auto *pw = getpwuid(getuid());
+        if (pw) home = pw->pw_dir;
+    }
+    std::string dir = (home ? home : "/tmp");
+    dir += "/.config/pwweb";
+    mkdir(dir.c_str(), 0755);
+    return dir;
+}
+
+std::string WebServer::readFile(const std::string &path) const {
+    std::ifstream f(path);
+    if (!f.is_open()) return "{}";
+    return std::string((std::istreambuf_iterator<char>(f)),
+                        std::istreambuf_iterator<char>());
+}
+
+void WebServer::writeFile(const std::string &path, const std::string &data) const {
+    std::ofstream f(path);
+    if (f.is_open()) f << data;
+}
+
 // ============================================================================
 // JSON serialization helpers
 // ============================================================================
@@ -309,6 +340,69 @@ void WebServer::setupRoutes() {
     };
     m_http.Options("/api/connect", cors_handler);
     m_http.Options("/api/disconnect", cors_handler);
+    m_http.Options("/api/positions", cors_handler);
+    m_http.Options("/api/patchbay", cors_handler);
+
+    // Positions persistence: GET /api/positions
+    m_http.Get("/api/positions", [this](const httplib::Request &, httplib::Response &res) {
+        std::string path = dataDir() + "/positions.json";
+        res.set_content(readFile(path), "application/json");
+        res.set_header("Access-Control-Allow-Origin", "*");
+    });
+
+    // Positions persistence: PUT /api/positions
+    m_http.Put("/api/positions", [this](const httplib::Request &req, httplib::Response &res) {
+        std::string path = dataDir() + "/positions.json";
+        writeFile(path, req.body);
+        res.set_content("{\"ok\":true}", "application/json");
+        res.set_header("Access-Control-Allow-Origin", "*");
+    });
+
+    // Patchbay: GET /api/patchbay
+    m_http.Get("/api/patchbay", [this](const httplib::Request &, httplib::Response &res) {
+        std::string path = dataDir() + "/patchbay.json";
+        res.set_content(readFile(path), "application/json");
+        res.set_header("Access-Control-Allow-Origin", "*");
+    });
+
+    // Patchbay: PUT /api/patchbay (save current connections as a named snapshot)
+    m_http.Put("/api/patchbay", [this](const httplib::Request &req, httplib::Response &res) {
+        std::string path = dataDir() + "/patchbay.json";
+        writeFile(path, req.body);
+        res.set_content("{\"ok\":true}", "application/json");
+        res.set_header("Access-Control-Allow-Origin", "*");
+    });
+
+    // Patchbay: POST /api/patchbay/apply (apply saved connections to current graph)
+    m_http.Post("/api/patchbay/apply", [this](const httplib::Request &req, httplib::Response &res) {
+        // req.body is a JSON array of {output_port_id, input_port_id} pairs
+        // We just parse it and connect each pair
+        // Simple parsing: find all pairs
+        std::string body = req.body;
+        size_t pos = 0;
+        int connected = 0;
+        while (pos < body.size()) {
+            uint32_t out_id = 0, in_id = 0;
+            int chars = 0;
+            if (sscanf(body.c_str() + pos,
+                    "{\"output_port_id\":%u,\"input_port_id\":%u}%n",
+                    &out_id, &in_id, &chars) == 2 ||
+                sscanf(body.c_str() + pos,
+                    "{\"output_port_id\":%u, \"input_port_id\":%u}%n",
+                    &out_id, &in_id, &chars) == 2)
+            {
+                if (m_engine.connectPorts(out_id, in_id))
+                    connected++;
+            }
+            pos = body.find('{', pos + 1);
+            if (pos == std::string::npos) break;
+        }
+        if (connected > 0) broadcastGraph();
+        char buf[64];
+        snprintf(buf, sizeof(buf), "{\"ok\":true,\"connected\":%d}", connected);
+        res.set_content(buf, "application/json");
+        res.set_header("Access-Control-Allow-Origin", "*");
+    });
 }
 
 // end of web_server.cpp