revert: remove level meters and VU meter feature

Reverts:
- fix: move VU meter above volume controls to stop blocking mute button
- Merge feature/graph-ux-meters (region fix, toggle, segmented VU meters)
- Merge feature/level-meters (pw_stream peak metering, /api/peaks)

VU meters / level meters don't belong in a patchbay.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/web_server.cpp

@@ -302,21 +302,6 @@ void WebServer::setupRoutes() {
         res.set_header("Access-Control-Allow-Origin", "*");
     });
 
-    // Level meters: GET /api/peaks → {"<node_id>": <linear_peak_0_1>, ...}
-    m_http.Get("/api/peaks", [this](const httplib::Request &, httplib::Response &res) {
-        auto peaks = m_engine.getPeaks();
-        std::string json = "{";
-        bool first = true;
-        for (auto &[id, peak] : peaks) {
-            if (!first) json += ",";
-            json += "\"" + std::to_string(id) + "\":" + std::to_string(peak);
-            first = false;
-        }
-        json += "}";
-        res.set_content(json, "application/json");
-        res.set_header("Access-Control-Allow-Origin", "*");
-    });
-
     // REST API: POST /api/connect
     m_http.Post("/api/connect", [this](const httplib::Request &req, httplib::Response &res) {
         uint32_t out_id = 0, in_id = 0;