sfu-signaling: real Janus signaling service implementation

- JanusClient.php: HTTP REST client for Janus Gateway API
- SfuRoomRepository.php: room + participant + stats persistence
- bootstrap.php: PDO, auth, Janus client factory
- public/index.php: front-controller routing
- public/health.php: Janus online check
- public/api/rooms.php: list/create/destroy rooms
- public/api/join.php: SDP offer relay → Janus VideoRoom
- public/api/stats.php: bitrate/packet-loss analytics ingest
- public/dashboard.php: SFU rooms UI (common BE dark-theme styles)

Co-authored-by: Cursor <cursoragent@cursor.com>

public/api/rooms.php

@@ -0,0 +1,60 @@
+<?php
+declare(strict_types=1);
+/**
+ * SFU rooms API
+ *  GET  /api/rooms          — list active rooms
+ *  POST /api/rooms          — create room  (body: {name, purpose})
+ *  DELETE /api/rooms/{id}   — close room
+ */
+require_once dirname(__DIR__, 2) . '/src/bootstrap.php';
+
+$user   = sfuRequireAuth();
+$method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
+$path   = trim(parse_url($_SERVER['REQUEST_URI'] ?? '', PHP_URL_PATH) ?? '', '/');
+$parts  = explode('/', $path);
+$roomId = (int) ($parts[array_key_last($parts)] ?? 0);
+
+$repo   = new \AndroidCast\Sfu\SfuRoomRepository(sfuPdo());
+$janus  = janusClient();
+
+if ($method === 'GET') {
+    sfuJsonOk(['rooms' => $repo->listActive()]);
+}
+
+if ($method === 'POST') {
+    $input = json_decode(file_get_contents('php://input'), true) ?? [];
+    $name  = trim((string) ($input['name'] ?? 'Room ' . date('H:i')));
+    $purp  = trim((string) ($input['purpose'] ?? 'screen_cast'));
+
+    /* Allocate a Janus session + handle to create the VideoRoom */
+    $sid = $janus->createSession();
+    if (!$sid) { sfuJsonErr('Janus unreachable'); }
+    $hid = $janus->attachVideoRoom($sid);
+    if (!$hid) { sfuJsonErr('Janus attach failed'); }
+
+    $janusRoomId = mt_rand(1_000_000, 9_999_999);
+    $ok = $janus->createRoom($sid, $hid, $janusRoomId, [
+        'description' => $name,
+        'videocodec'  => 'vp8,h264',
+        'audiocodec'  => 'opus',
+        'bitrate'     => 1024000,
+    ]);
+    if (!$ok) { sfuJsonErr('Janus room creation failed'); }
+
+    $id = $repo->createRoom($janusRoomId, (int) $user['id'], $name, $purp);
+    sfuJsonOk(['room' => ['id' => $id, 'janus_room_id' => $janusRoomId, 'name' => $name]]);
+}
+
+if ($method === 'DELETE' && $roomId > 0) {
+    $row = $repo->getByJanusId($roomId) ?? sfuJsonErr('room not found', 404);
+    /* Best-effort Janus destroy */
+    $sid = $janus->createSession();
+    if ($sid) {
+        $hid = $janus->attachVideoRoom($sid);
+        if ($hid) { $janus->destroyRoom($sid, $hid, $roomId); }
+    }
+    $repo->closeRoom((int) $row['id']);
+    sfuJsonOk(['destroyed' => true]);
+}
+
+sfuJsonErr('method not allowed', 405);