Improve release scripts and make workflows manual

Redirect script informational/warning output to stderr and improve robustness of release tooling. Changes include:

- Redirect many echo messages to stderr so scripts can emit machine-readable output on stdout.
- Extract-release-notes: better parsing of CHANGELOG entries (tries v-prefixed and non-prefixed headings, cleaner note formatting) and improved fallbacks when changelog is missing.
- Extract-version: accept versions with +build or -suffix, add diagnostic output when pubspec is missing, and tighten validation.
- Setup/verify APK signing: more consistent stderr logging and clearer warnings; ensure keystore decoding/logging is visible.
- Minor script usage message fixes (generate-tag-name, attach-apk-to-release).
- CI/workflows: change backend-foundation, mobile-ci, and web-quality triggers to workflow_dispatch (manual runs); update product-release (make scripts step label emoji, remove node cache lines, bump Flutter to 3.38.x).

These changes improve CI reliability, make scripts friendlier for automated consumers, and fix release note/version parsing edge cases.

.github/scripts/attach-apk-to-release.sh

@@ -28,8 +28,8 @@ VERSION="$4"
 ENV="$5"
 
 if [ -z "$TAG_NAME" ] || [ -z "$APP" ] || [ -z "$APP_NAME" ] || [ -z "$VERSION" ] || [ -z "$ENV" ]; then
-    echo "❌ Error: Missing required arguments"
-    echo "Usage: $0 <tag_name> <app> <app_name> <version> <environment>"
+    echo "❌ Error: Missing required arguments" >&2
+    echo "Usage: $0 <tag_name> <app> <app_name> <version> <environment>" >&2
     exit 1
 fi
 
@@ -37,8 +37,8 @@ fi
 APK_PATH="apps/mobile/apps/${APP_NAME}/build/app/outputs/flutter-apk/app-release.apk"
 
 if [ ! -f "$APK_PATH" ]; then
-    echo "❌ Error: APK not found at $APK_PATH"
-    echo "Searching for APK files..."
+    echo "❌ Error: APK not found at $APK_PATH" >&2
+    echo "Searching for APK files..." >&2
     find apps/mobile/apps/${APP_NAME} -name "*.apk"
     exit 1
 fi
@@ -54,7 +54,7 @@ fi
 cp "$APK_PATH" "/tmp/$APK_NAME"
 
 # Upload to GitHub Release
-echo "📤 Uploading $APK_NAME to release $TAG_NAME..."
+echo "📤 Uploading $APK_NAME to release $TAG_NAME..." >&2
 gh release upload "$TAG_NAME" "/tmp/$APK_NAME" --clobber
 
-echo "✅ APK attached to release: $APK_NAME"
+echo "✅ APK attached to release: $APK_NAME" >&2