fix(playback): canonicalize base URL scheme case

FFmpeg's protocol lookup is case-sensitive, so a stored "Https://" base
URL reaches mpv verbatim through the direct-play string concat and fails
with "Protocol not found" (API calls survive because Dart's Uri
lowercases the scheme). Canonicalize at Jellyfin URL intake and in the
connection constructor so persisted configs self-heal on load, and
register mpv-escaped (https\://) redaction variants so option-value
logs stop leaking the server host.

close #1465

test/utils/log_redaction_manager_test.dart

@@ -177,6 +177,16 @@ void main() {
       expect(r1.contains('server.example.com'), isFalse);
       expect(r2.contains('server.example.com'), isFalse);
     });
+
+    test('redacts the mpv-escaped form used in option-value logs', () {
+      LogRedactionManager.registerServerUrl('https://server.example.com');
+      // mpv echoes list options like sub-files with ':' escaped as '\:'.
+      final result = LogRedactionManager.redact(
+        r"Setting option 'sub-files' = 'https\://server.example.com/Videos/1/Subtitles/0/0/Stream.srt' (flags = 16)",
+      );
+      expect(result.contains('server.example.com'), isFalse);
+      expect(result.contains('[REDACTED_URL]'), isTrue);
+    });
   });
 
   group('registerCustomValue', () {

test/utils/url_utils_test.dart

@@ -0,0 +1,38 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/utils/url_utils.dart';
+
+void main() {
+  group('stripTrailingSlash', () {
+    test('removes a single trailing slash', () {
+      expect(stripTrailingSlash('https://host/'), 'https://host');
+    });
+
+    test('trims whitespace and leaves slashless input unchanged', () {
+      expect(stripTrailingSlash('  https://host  '), 'https://host');
+      expect(stripTrailingSlash(''), '');
+    });
+  });
+
+  group('canonicalizeBaseUrl', () {
+    test('lowercases a mixed-case scheme (#1465)', () {
+      // FFmpeg's protocol lookup is case-sensitive; "Https://" reaching the
+      // player as a raw string fails with "Protocol not found".
+      expect(canonicalizeBaseUrl('Https://jellyfin.example.com'), 'https://jellyfin.example.com');
+      expect(canonicalizeBaseUrl('HTTPS://jellyfin.example.com'), 'https://jellyfin.example.com');
+    });
+
+    test('only touches the scheme, not host/path/query', () {
+      expect(canonicalizeBaseUrl('HTTP://Host.Example.com:8096/JellyFin'), 'http://Host.Example.com:8096/JellyFin');
+    });
+
+    test('strips trailing slash and trims whitespace', () {
+      expect(canonicalizeBaseUrl(' Https://host:8096/jellyfin/ '), 'https://host:8096/jellyfin');
+    });
+
+    test('leaves schemeless input unchanged', () {
+      expect(canonicalizeBaseUrl('host:8096'), 'host:8096');
+      expect(canonicalizeBaseUrl('Host.example.com'), 'Host.example.com');
+      expect(canonicalizeBaseUrl(''), '');
+    });
+  });
+}