build: CI and the snap build with Flutter v3.47.8, as the laptop does

A patch release; the release tool refuses to build with another Flutter
than CI tests with.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

.forgejo/workflows/ci.yaml

@@ -23,7 +23,7 @@ jobs:
     timeout-minutes: 45
     env:
       # The Flutter the app is developed with; move it together with the local one.
-      FLUTTER_VERSION: 3.47.5
+      FLUTTER_VERSION: 3.47.8
       # The Serverpod CLI, for the generated-code check: the servers' Serverpod version
       # (every package pins it; the root's tests hold it to the lock); move it together
       # with them.

README.md

@@ -35,7 +35,7 @@ One pub workspace holds every package: one `pubspec.lock`, one version of each d
 
 ## Getting started
 
-- **Flutter v3.47.5**, the version CI uses (`FLUTTER_VERSION` in
+- **Flutter v3.47.8**, the version CI uses (`FLUTTER_VERSION` in
   `.forgejo/workflows/ci.yaml`), with each platform you build for set up by Flutter's own
   guides; what an app needs beyond that is in its README.
 - **The Serverpod CLI v4.0.4**: `dart install serverpod_cli@4.0.4`. Pass

apps/learn/README.md

@@ -42,7 +42,7 @@ instance's basics; a Serverpod module), `halkyon_app` (instances, sign-in, sync)
 
 ## Setting up
 
-- **Flutter v3.47.5**, the version CI uses (`FLUTTER_VERSION` in
+- **Flutter v3.47.8**, the version CI uses (`FLUTTER_VERSION` in
   `.forgejo/workflows/ci.yaml`). Set up each platform you build for with Flutter's own
   guides: [Linux](https://docs.flutter.dev/platform-integration/linux/setup),
   [Windows](https://docs.flutter.dev/platform-integration/windows/setup),

snap/snapcraft.yaml

@@ -83,7 +83,7 @@ parts:
   flutter:
     plugin: nil
     source: https://github.com/flutter/flutter.git
-    source-tag: '3.47.5'
+    source-tag: '3.47.8'
     source-depth: 1
     build-packages:
       - clang