feat(app): scan a printed seed label back into its record

Closes the physical↔digital loop the labels opened: the QR on a printed
envelope (tane://seed, already encoded by seed_label_codec) can now be
scanned from the inventory bar. A known label opens its variety; an
unknown one asks before adding anything, then creates the variety (species
linked by exact scientific name when bundled) with a lot carrying the
label's year and origin. Scanner is pure ZXing (zxing_barcode_scanner,
MIT) — no ML Kit, no Play Services, F-Droid-safe, the stack Ğ1nkgo ships.
Mobile-only; other platforms don't show the button (OCR precedent).
The post-scan flow is a plain function (handleScannedPayload) so it's
widget-tested without a camera.

docs/fdroid/org.comunes.tane.yml

@@ -15,38 +15,30 @@ AutoName: Tane
 RepoType: git
 Repo: https://git.comunes.org/comunes/tane.git
 
-Builds:
-  - versionName: 0.1.0
-    versionCode: 2
-    commit: v0.1.0
-    subdir: apps/app_seeds
-    sudo:
-      - apt-get update
-      - apt-get install -y git unzip xz-utils
-      - git clone --depth 1 -b 3.41.9 https://github.com/flutter/flutter.git /opt/flutter
-      - chown -R vagrant:vagrant /opt/flutter
-    output: build/app/outputs/flutter-apk/app-release.apk
-    prebuild:
-      - export PATH="/opt/flutter/bin:$PATH"
-      - git config --global --add safe.directory /opt/flutter
-      - flutter config --no-analytics
-      - flutter pub get
-      - dart run slang
-      - dart run build_runner build --delete-conflicting-outputs
-    build:
-      - export PATH="/opt/flutter/bin:$PATH"
-      - flutter build apk --release
+# Reproducible, developer-signed builds: F-Droid rebuilds from source and, if the
+# output matches our own signed APK on git.comunes.org byte-for-byte, publishes
+# OUR APK. Same signature as the Google Play build, so users move between stores
+# without reinstalling. The fingerprint below is the SHA-256 of the tane-upload
+# signing certificate (public value); the keystore/passwords never leave CI.
+AllowedAPKSigningKeys: ddfae432091b8248a8a4a1b353487fa626301f4357ef835e94ec312f69418e38
 
-  - versionName: 0.1.1
-    versionCode: 3
-    commit: v0.1.1
+# One build entry per ABI: `flutter build --split-per-abi` yields smaller APKs and
+# each split carries a distinct versionCode (gradle: versionCode*10 + {arm-v7a:1,
+# arm64:2, x86_64:3}), so v0.1.2 (+4) -> 41/42/43. The `binary:` is the reference
+# APK F-Droid verifies against, uploaded to the Forgejo release by
+# .forgejo/workflows/release.yml on the `v*` tag.
+Builds:
+  - versionName: 0.1.2
+    versionCode: 41
+    commit: v0.1.2
     subdir: apps/app_seeds
     sudo:
       - apt-get update
       - apt-get install -y git unzip xz-utils
       - git clone --depth 1 -b 3.41.9 https://github.com/flutter/flutter.git /opt/flutter
       - chown -R vagrant:vagrant /opt/flutter
-    output: build/app/outputs/flutter-apk/app-release.apk
+    output: build/app/outputs/flutter-apk/app-armeabi-v7a-release.apk
+    binary: https://git.comunes.org/comunes/tane/releases/download/v%v/app-armeabi-v7a-release.apk
     prebuild:
       - export PATH="/opt/flutter/bin:$PATH"
       - git config --global --add safe.directory /opt/flutter
@@ -56,10 +48,54 @@ Builds:
       - dart run build_runner build --delete-conflicting-outputs
     build:
       - export PATH="/opt/flutter/bin:$PATH"
-      - flutter build apk --release
+      - flutter build apk --release --split-per-abi --target-platform=android-arm
+
+  - versionName: 0.1.2
+    versionCode: 42
+    commit: v0.1.2
+    subdir: apps/app_seeds
+    sudo:
+      - apt-get update
+      - apt-get install -y git unzip xz-utils
+      - git clone --depth 1 -b 3.41.9 https://github.com/flutter/flutter.git /opt/flutter
+      - chown -R vagrant:vagrant /opt/flutter
+    output: build/app/outputs/flutter-apk/app-arm64-v8a-release.apk
+    binary: https://git.comunes.org/comunes/tane/releases/download/v%v/app-arm64-v8a-release.apk
+    prebuild:
+      - export PATH="/opt/flutter/bin:$PATH"
+      - git config --global --add safe.directory /opt/flutter
+      - flutter config --no-analytics
+      - flutter pub get
+      - dart run slang
+      - dart run build_runner build --delete-conflicting-outputs
+    build:
+      - export PATH="/opt/flutter/bin:$PATH"
+      - flutter build apk --release --split-per-abi --target-platform=android-arm64
+
+  - versionName: 0.1.2
+    versionCode: 43
+    commit: v0.1.2
+    subdir: apps/app_seeds
+    sudo:
+      - apt-get update
+      - apt-get install -y git unzip xz-utils
+      - git clone --depth 1 -b 3.41.9 https://github.com/flutter/flutter.git /opt/flutter
+      - chown -R vagrant:vagrant /opt/flutter
+    output: build/app/outputs/flutter-apk/app-x86_64-release.apk
+    binary: https://git.comunes.org/comunes/tane/releases/download/v%v/app-x86_64-release.apk
+    prebuild:
+      - export PATH="/opt/flutter/bin:$PATH"
+      - git config --global --add safe.directory /opt/flutter
+      - flutter config --no-analytics
+      - flutter pub get
+      - dart run slang
+      - dart run build_runner build --delete-conflicting-outputs
+    build:
+      - export PATH="/opt/flutter/bin:$PATH"
+      - flutter build apk --release --split-per-abi --target-platform=android-x64
 
 AutoUpdateMode: Version
 UpdateCheckMode: Tags v[\d.]+
 UpdateCheckData: apps/app_seeds/pubspec.yaml|version:\s*[\d.]+\+(\d+)|apps/app_seeds/pubspec.yaml|version:\s*([\d.]+)\+
-CurrentVersion: 0.1.1
-CurrentVersionCode: 3
+CurrentVersion: 0.1.2
+CurrentVersionCode: 43