Merge PR #13 with gzip-only WebConfig assets

Keep the graceful final-ACK TCP close and optional FEM control guards from
pixitha's browser compatibility fixes. Replace Brotli negotiation and duplicate
page assets with one gzip representation compressed by Google Zopfli 0.4.3
using 1,000 iterations. Compress the bootstrap, captive success, compact OTA,
and static WiFi setup pages with the same validated build cache.

Honor gzip quality values and wildcard precedence. Validate compressed OTA
page evidence in the firmware capability gate, and add native and Python
regressions plus CI coverage. Remove the unused Brotli build dependency.

Validation: 54 native tests, 56 Python/browser checks, full V4.3 build and
verified application flash. Actual V4 WiFi responses matched the generated
gzip assets; 30 repeat downloads completed without reboot. Chromium loaded
the setup and settings pages without script or transfer errors. Physical
Android testing is pending because the Pi detects no phone over USB or mDNS.

test/test_webconfig_ui_runtime.py

@@ -2,7 +2,7 @@
 
 """Optional real-browser checks for WebConfig's asynchronous setup races."""
 
-import brotli
+import gzip
 import json
 import os
 from pathlib import Path
@@ -68,12 +68,12 @@ def run_browser(args):
 
 def embedded_page():
     header = HEADER.read_text(encoding="utf-8")
-    length = int(re.search(r"WEBCONFIG_HTML_BR_LEN = (\d+);", header).group(1))
-    array = header.split("const uint8_t WEBCONFIG_HTML_BR[] PROGMEM = {", 1)[1]
+    length = int(re.search(r"WEBCONFIG_HTML_GZ_LEN = (\d+);", header).group(1))
+    array = header.split("const uint8_t WEBCONFIG_HTML_GZ[] PROGMEM = {", 1)[1]
     blob = bytes(
         int(value, 16) for value in re.findall(r"0x([0-9a-f]{2})", array)
     )[:length]
-    return brotli.decompress(blob).decode("utf-8")
+    return gzip.decompress(blob).decode("utf-8")
 
 
 class WebConfigUiRuntimeTest(unittest.TestCase):