Merge upstream/main into feat/webui-compression

Resolve conflicts against ~55 upstream commits since 37eefb4:
- Makefile: keep upstream parallel-build fixes (machine_init.c, SUBDIRSCLEAN, html_data grouped target) and retain minify+gzip pipeline (-z, html_min, .css/.ico)
- tools: retain gzip support (zlib, -lz) lost in upstream revert
- httpd/httpd.c: keep Content-Encoding: gzip alongside upstream GET walk, config upload, syslog/hostname changes
- html: port upstream HTML/JS changes into SPA (single-page) bundle:
  * i18n: add port_col_devices / port_devices keys (en/ja/zh)
  * ports: add Connected devices column, devRender/devWalk via walkL2 (8c3df64)
  * config: add syslog port, extended stp/igmp/bw patterns, conf_toggle handling
  * system: show /cmd output in console (console_out), 401 handling
  * l2: hide delete for CPU entry, delL2Button, sort/filter improvements
  * navigation: add STP entry
- SPA: integrate new STP page (stp.html/js) as page-stp section with sectionInits.stp, bridge/prio handling, per-port config/status tables
- Remove per-page HTML/JS files (now bundled) and standalone stp.html/js

Verified: tools build, html_min generation (main.js 93k->81k->19k gzip, 8 files), html_data.h gzip sizes, main.js syntax check.

html/index.html

@@ -49,7 +49,7 @@
     <div class="page" id="page-ports" style="margin-left:16%;padding:1px 16px;height:1000px;">
       <h1 data-i18n="port_heading">Port Configuration</h1>
       <table id="speedtable">
-        <tr> <th data-i18n="port_col_port">Port</th> <th data-i18n="port_col_name">Name</th> <th data-i18n="port_col_speed">Current Link Speed</th><th data-i18n="port_col_set_speed">Set Speed</th><th data-i18n="port_col_disabled">Disabled</th><th data-i18n="port_col_apply">Apply</th></tr>
+        <tr> <th data-i18n="port_col_port">Port</th> <th data-i18n="port_col_name">Name</th> <th data-i18n="port_col_speed">Current Link Speed</th><th data-i18n="port_col_devices">Connected devices</th><th data-i18n="port_col_set_speed">Set Speed</th><th data-i18n="port_col_disabled">Disabled</th><th data-i18n="port_col_apply">Apply</th></tr>
       </table>
       <h2 style="margin-top:3em" data-i18n="port_mtu_heading">Configure Maximum Frame Size (MTU) forwarded at Port</h2>
       <table id="mtutable" style="margin-top:1em">
@@ -132,6 +132,40 @@
       </table>
     </div>
 
+    <div class="page" id="page-stp" style="margin-left:16%;padding:1px 16px;height:1000px;">
+      <h1>Spanning Tree (RSTP)</h1>
+      <h2>Mode: <select id="stpMode"><option value="off">Disabled</option><option value="on">Enabled</option></select>
+        <input style="width:15%;margin-left: 3em;" class="action" id="stp_sub" onclick="stpSub();" type="button" value="Apply"></h2>
+      <div id="stpStat" style="font-family:monospace;"></div>
+      <h2>Bridge settings</h2>
+      <table id="stpBridge">
+        <tr>
+          <th>Priority</th><th>Version</th><th>Hello [s]</th><th>Max age [s]</th><th>Fwd delay [s]</th><th>Tx hold</th>
+        </tr>
+        <tr>
+          <td><select id="bPrio"></select></td>
+          <td><select id="bVer"><option value="rstp">RSTP</option><option value="stp">STP compat</option></select></td>
+          <td><input id="bHello" type="number" min="1" max="10" style="width:4em"></td>
+          <td><input id="bMaxage" type="number" min="6" max="40" style="width:4em"></td>
+          <td><input id="bFwd" type="number" min="4" max="30" style="width:4em"></td>
+          <td><input id="bTxhold" type="number" min="1" max="10" style="width:4em"></td>
+        </tr>
+      </table>
+      <p style="font-size:small">Changes apply immediately. Edge ports skip the listen period; guard/filter act on received BPDUs.</p>
+      <h2>Port configuration</h2>
+      <table id="stpPortsTbl">
+        <tr>
+          <th>Port</th><th>State</th><th>Path Cost<br><span style="font-weight:normal;font-size:small">(0 = Auto)</span></th><th>Priority</th><th>Edge Port</th><th>BPDU Filter</th><th>Guard</th><th>Point-to-Point</th>
+        </tr>
+      </table>
+      <h2>Port status</h2>
+      <table id="stpStatTbl">
+        <tr>
+          <th>Port</th><th>Port State</th><th>Role</th><th>Designated Bridge</th><th>Designated Port ID</th><th>Designated Cost</th><th>Oper. Edge</th><th>Oper. P2P</th>
+        </tr>
+      </table>
+    </div>
+
     <div class="page" id="page-mirror" style="margin-left:16%;padding:1px 16px;height:1000px;">
       <h1 data-i18n="mirror_heading">Mirror Configuration</h1>
       <label class="tswitch"><span data-i18n="mirror_enabled">Enabled:</span> <input id="me" type="checkbox"></label><br/>
@@ -258,6 +292,8 @@
         <input style="width:20%;" class="action" id="cmd_sub" onclick="cmdSub();" type="button" data-i18n="sys_send_cmd" value="Send Command"><br/>
         <br/><br/> 
         <span data-i18n="sys_console_warn">Be careful when entering console commands, you can lock yourself out!</span><br/>
+        <br/>
+        <pre id="console_out" style="height:22em;overflow:auto;white-space:pre-wrap;border:1px solid;padding:0.5em;"></pre>
       </div>
     </div>