Add separate license info widget for CC BY-SA notice

lib/widgets/add_exercise/license_info_widget.dart

@@ -0,0 +1,77 @@
+import 'package:flutter/material.dart';
+import 'package:url_launcher/url_launcher.dart';
+import 'package:wger/l10n/generated/app_localizations.dart';
+
+/// Static widget displaying CC BY-SA 4.0 license notice for image uploads
+///
+/// This widget informs users that by uploading images, they agree to release
+/// them under the CC BY-SA 4.0 license. The license name is clickable and
+/// opens the Creative Commons license page.
+///
+/// Being a separate widget allows Flutter to optimize rendering since
+/// this content never changes.
+class LicenseInfoWidget extends StatelessWidget {
+  const LicenseInfoWidget({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+
+    return Container(
+      padding: const EdgeInsets.all(12),
+      decoration: BoxDecoration(
+        color: colorScheme.surfaceVariant,
+        borderRadius: BorderRadius.circular(4),
+        border: Border.all(color: colorScheme.outline),
+      ),
+      child: Row(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Icon(
+            Icons.info_outline,
+            size: 20,
+            color: colorScheme.onSurfaceVariant,
+          ),
+          const SizedBox(width: 8),
+          Expanded(
+            child: RichText(
+              text: TextSpan(
+                style: TextStyle(
+                  fontSize: 12,
+                  color: colorScheme.onSurfaceVariant,
+                ),
+                children: [
+                  TextSpan(
+                    text: AppLocalizations.of(context).imageDetailsLicenseNoticePrefix,
+                  ),
+                  WidgetSpan(
+                    child: GestureDetector(
+                      onTap: () async {
+                        final url = Uri.parse('https://creativecommons.org/licenses/by-sa/4.0/');
+                        if (await canLaunchUrl(url)) {
+                          await launchUrl(url, mode: LaunchMode.externalApplication);
+                        }
+                      },
+                      child: Text(
+                        'CC BY-SA 4.0',
+                        style: TextStyle(
+                          fontSize: 12,
+                          color: colorScheme.primary,
+                          fontWeight: FontWeight.bold,
+                          decoration: TextDecoration.underline,
+                        ),
+                      ),
+                    ),
+                  ),
+                  TextSpan(
+                    text: AppLocalizations.of(context).imageDetailsLicenseNoticeSuffix,
+                  ),
+                ],
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}