feat: implement togglable debug log streaming for server stdout/stderr and client console logs

- Created server/utils/logCapture.js to intercept and buffer server output, stripping ANSI escape codes.
- Created server/middleware/logStreamAuth.js enforcing subnet IP filtering (LOG_ALLOW_SUBNETS), Emby session cookie, Basic Auth fallback, and X-Webhook-Secret header bypass.
- Created server/routes/debug.js with SSE streams /api/debug/server-logs, /api/debug/client-logs and batched POST /api/debug/client-logs. Exposes public configuration status at /api/debug/status.
- Integrated log capture and mounted debug routes in server/app.js and server/index.js.
- Implemented client/src/utils/clientLogCapture.js in the frontend SPA to hook console log/warn/error and flush batched console events.
- Documented all endpoints in OpenAPI server/openapi.yaml, ARCHITECTURE.md, and README.md.
- Wrote route integration tests and frontend console capture tests, with full validation in swagger-coverage.

server/utils/logCapture.js

@@ -0,0 +1,131 @@
+// Copyright (c) 2026 Gordon Bolton. MIT License.
+const EventEmitter = require('events');
+
+class LogEmitter extends EventEmitter {}
+const logEmitter = new LogEmitter();
+
+const logBuffer = [];
+const clientLogBuffer = [];
+const MAX_BUFFER_SIZE = 1000;
+
+// ANSI escape code regular expression for stripping terminal colors
+const ansiRegex = /[\u001b\u009b][[()#;?]*(?:[0-9]{1,4}(?:;[0-9]{0,4})*)?[0-9A-ORZcf-nqry=><]/g;
+
+function stripAnsi(str) {
+  return typeof str === 'string' ? str.replace(ansiRegex, '') : str;
+}
+
+// Keep track of original stdout/stderr write functions
+const originalStdoutWrite = process.stdout.write;
+const originalStderrWrite = process.stderr.write;
+
+// Buffer to accumulate partial lines from stdout and stderr
+let stdoutLineBuffer = '';
+let stderrLineBuffer = '';
+
+function processStreamData(data, encoding, callback, streamName, lineAccumulator) {
+  let str = '';
+  if (Buffer.isBuffer(data)) {
+    str = data.toString(encoding || 'utf8');
+  } else if (typeof data === 'string') {
+    str = data;
+  }
+
+  // Delegate writing to the original stream first
+  callback.call(this, data, encoding);
+
+  // Append new data to the accumulator
+  const accumulated = lineAccumulator.buffer + str;
+  const lines = accumulated.split(/\r?\n/);
+
+  // The last element is either empty (if str ended with \n) or a partial line
+  lineAccumulator.buffer = lines.pop();
+
+  for (const line of lines) {
+    const cleanLine = stripAnsi(line);
+    if (!cleanLine) continue;
+
+    // Prepend timestamp if not present (format: [ISO] Message)
+    const timestampedLine = cleanLine.startsWith('[') 
+      ? cleanLine 
+      : `[${new Date().toISOString()}] [${streamName.toUpperCase()}] ${cleanLine}`;
+
+    logBuffer.push(timestampedLine);
+    if (logBuffer.length > MAX_BUFFER_SIZE) {
+      logBuffer.shift();
+    }
+
+    logEmitter.emit('server-log', timestampedLine);
+  }
+}
+
+// Accumulator objects to allow updating string buffers by reference
+const stdoutAccumulator = { buffer: '' };
+const stderrAccumulator = { buffer: '' };
+
+let isHooked = false;
+
+function init() {
+  if (isHooked) return;
+
+  // Intercept stdout
+  process.stdout.write = function(data, encoding, callback) {
+    processStreamData.call(
+      process.stdout,
+      data,
+      encoding,
+      originalStdoutWrite,
+      'stdout',
+      stdoutAccumulator
+    );
+    if (typeof callback === 'function') callback();
+    return true;
+  };
+
+  // Intercept stderr
+  process.stderr.write = function(data, encoding, callback) {
+    processStreamData.call(
+      process.stderr,
+      data,
+      encoding,
+      originalStderrWrite,
+      'stderr',
+      stderrAccumulator
+    );
+    if (typeof callback === 'function') callback();
+    return true;
+  };
+
+  isHooked = true;
+}
+
+/**
+ * Ingests a list of client-side logs into the rolling clientLogBuffer.
+ * Each client log is expected to have structure: { timestamp, level, message }
+ */
+function ingestClientLogs(logs) {
+  if (!Array.isArray(logs)) return;
+
+  for (const log of logs) {
+    const timestamp = log.timestamp || new Date().toISOString();
+    const level = (log.level || 'info').toUpperCase();
+    const msg = typeof log.message === 'string' ? log.message : JSON.stringify(log.message);
+
+    const formattedLog = `[${timestamp}] [CLIENT] [${level}] ${stripAnsi(msg)}`;
+    clientLogBuffer.push(formattedLog);
+
+    if (clientLogBuffer.length > MAX_BUFFER_SIZE) {
+      clientLogBuffer.shift();
+    }
+
+    logEmitter.emit('client-log', formattedLog);
+  }
+}
+
+module.exports = {
+  init,
+  logEmitter,
+  logBuffer,
+  clientLogBuffer,
+  ingestClientLogs
+};