Replace git patch with portable shell script and parameterize OpenWrt version

- Convert enable_wcn36xx_mac80211.patch to apply_patches.sh (sed + heredoc)
  for cross-version compatibility (old patch moved to TBR/)
- GHA workflows auto-resolve latest OpenWrt 25.12.x tag via git ls-remote
- Unify build.yml and build-all.yml into single workflow with dynamic matrix
- Local dev (Dockerfile/docker-compose) defaults to main (snapshot)
- Remove target-specific APK feed on first boot (msm89xx not on downloads.openwrt.org)
- Make LuCI odhcpd fix conditional
- Update README with new build instructions

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

devenv/docker-compose.yml

@@ -13,6 +13,8 @@ services:
     build:
       context: ..
       dockerfile: devenv/Dockerfile
+      args:
+        OPENWRT_VERSION: ${OPENWRT_VERSION:-main}
     container_name: openwrt-builder
     working_dir: /home/builder/openwrt
     stdin_open: true