chore(android): de-anchor ANDROID_PLAN.md from the docs, re-enable the APK workflow

Reword every code comment and doc that referenced ANDROID_PLAN.md or its stage anchors (§E, G-step-0, O1) so the living docs no longer depend on the plan file: .claude/CLAUDE.md, deploy/README.md, docs/ARCHITECTURE.md, docs/TESTING.md, ui/README.md, ui/android/.gitignore, ui/e2e/native.spec.ts, ui/src/lib/netstate.ts.

Re-enable the manual signed-APK workflow (android-build.yaml.disabled -> android-build.yaml; the CI host already has the Android SDK; workflow_dispatch-only, so it does not auto-run on this PR). Add docs/ICONS.md — the single-master icon/logo format reference (web, PWA, Android, future iOS, store listings).

.gitea/workflows/android-build.yaml

@@ -5,9 +5,9 @@
 #
 # Signing degrades gracefully: with the ANDROID_KEYSTORE_* secrets present the APK is signed; without
 # them build.gradle produces an UNSIGNED release APK (so a dry run still proves the whole pipeline).
-# The keystore is a publication prerequisite — see deploy/README.md (Android build/release runbook) and
-# ANDROID_PLAN.md §E. The toolchain is self-provisioned here (JDK 21 + a cached Android SDK), so the
-# runner host needs nothing pre-installed.
+# The keystore is a publication prerequisite — see deploy/README.md (Android build/release runbook).
+# The toolchain is self-provisioned here (JDK 21 + a cached Android SDK), so the runner host needs
+# nothing pre-installed.
 name: android-build
 run-name: "android build ${{ github.sha }}"