Release signing fix + Obtainium install guide + publish script

- Fix withReleaseSigning: RN template's unconditional debug signingConfig was
  overriding the release key. Now uses the release key when BBP_UPLOAD_* is set
  (verified: APK signed CN=BigBrainParking), else debug.
- INSTALL.md: dead-simple Obtainium setup (one-tap obtainium:// link + manual
  Forgejo-source steps). README links it.
- scripts/publish-release.sh: create a Forgejo release + upload the signed APK.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/publish-release.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+# Publish a signed APK as a Forgejo release so Obtainium can track it.
+#
+# Prereqs:
+#   - A signed APK built at ./BigBrainParking-v<version>.apk (see docs/DISTRIBUTION.md)
+#   - A Forgejo token with repo write scope, in $FORGEJO_TOKEN or .keys/forgejo.token
+#     (create at: git.mowden.top -> Settings -> Applications -> Generate Token, scope: repository)
+#
+# Usage:  ./scripts/publish-release.sh
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+REPO="hank/BigBrainParking"
+API="https://git.mowden.top/api/v1"
+TOKEN="${FORGEJO_TOKEN:-$(cat .keys/forgejo.token 2>/dev/null || true)}"
+[ -n "$TOKEN" ] || { echo "ERROR: set FORGEJO_TOKEN or put a token in .keys/forgejo.token"; exit 1; }
+
+VERSION="$(node -e "console.log(require('./app/app.json').expo.version)")"
+TAG="v$VERSION"
+APK="BigBrainParking-$TAG.apk"
+[ -f "$APK" ] || { echo "ERROR: $APK not found — build a signed release first"; exit 1; }
+
+echo "Publishing $TAG ($APK)…"
+
+# Create the release (also creates the git tag on main if missing).
+REL="$(curl -sf -X POST "$API/repos/$REPO/releases" \
+  -H "Authorization: token $TOKEN" -H "Content-Type: application/json" \
+  -d "{\"tag_name\":\"$TAG\",\"target_commitish\":\"main\",\"name\":\"BigBrainParking $TAG\",\"body\":\"Unofficial ParkSmarter client for GrapheneOS. Install/update via Obtainium.\"}")"
+ID="$(printf '%s' "$REL" | node -e "let s='';process.stdin.on('data',d=>s+=d).on('end',()=>console.log(JSON.parse(s).id||''))")"
+[ -n "$ID" ] || { echo "ERROR: release create failed: $REL"; exit 1; }
+
+# Upload the APK asset.
+curl -sf -X POST "$API/repos/$REPO/releases/$ID/assets?name=$APK" \
+  -H "Authorization: token $TOKEN" -F "attachment=@$APK" >/dev/null
+
+echo "✓ Published: https://git.mowden.top/$REPO/releases/tag/$TAG"