feat: remote manifest model and content dependencies

Add http, crypto, path_provider deps; introduce RemoteManifest /
ManifestSeason immutable models with fromJson/toJson, schema-version
guard (FormatException on unsupported schema), and fallback for missing
current field. 3/3 TDD tests pass, flutter analyze clean.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/data/remote/manifest.dart

@@ -0,0 +1,71 @@
+/// Index of remotely available seasons, served as a static JSON next to the
+/// pack files. The client compares (seasonId, version) against its cache.
+class RemoteManifest {
+  const RemoteManifest({
+    required this.schemaVersion,
+    required this.minAppBuild,
+    required this.current,
+    required this.seasons,
+  });
+
+  static const int supportedSchema = 1;
+
+  factory RemoteManifest.fromJson(Map<String, dynamic> json) {
+    final schema = json['schemaVersion'] as int;
+    if (schema > supportedSchema) {
+      throw FormatException('Unsupported manifest schema: $schema');
+    }
+    final seasons = [
+      for (final s in json['seasons'] as List)
+        ManifestSeason.fromJson(s as Map<String, dynamic>),
+    ];
+    return RemoteManifest(
+      schemaVersion: schema,
+      minAppBuild: (json['minAppBuild'] as int?) ?? 1,
+      current: (json['current'] as String?) ??
+          (seasons.isNotEmpty ? seasons.last.seasonId : ''),
+      seasons: seasons,
+    );
+  }
+
+  final int schemaVersion;
+  final int minAppBuild;
+  final String current;
+  final List<ManifestSeason> seasons;
+
+  Map<String, dynamic> toJson() => {
+        'schemaVersion': schemaVersion,
+        'minAppBuild': minAppBuild,
+        'current': current,
+        'seasons': [for (final s in seasons) s.toJson()],
+      };
+}
+
+class ManifestSeason {
+  const ManifestSeason({
+    required this.seasonId,
+    required this.version,
+    required this.packUrl,
+    required this.sha256,
+  });
+
+  factory ManifestSeason.fromJson(Map<String, dynamic> json) =>
+      ManifestSeason(
+        seasonId: json['seasonId'] as String,
+        version: json['version'] as int,
+        packUrl: json['packUrl'] as String,
+        sha256: json['sha256'] as String,
+      );
+
+  final String seasonId;
+  final int version;
+  final String packUrl;
+  final String sha256;
+
+  Map<String, dynamic> toJson() => {
+        'seasonId': seasonId,
+        'version': version,
+        'packUrl': packUrl,
+        'sha256': sha256,
+      };
+}

pubspec.lock

@@ -146,7 +146,7 @@ packages:
     source: hosted
     version: "1.15.1"
   crypto:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: crypto
       sha256: c8ea0233063ba03258fbcf2ca4d6dadfefe14f02fab57702265467a19f27fadf
@@ -246,7 +246,7 @@ packages:
     source: hosted
     version: "2.1.3"
   http:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: http
       sha256: "87721a4a50b19c7f1d49001e51409bddc46303966ce89a65af4f4e6004896412"
@@ -390,7 +390,7 @@ packages:
     source: hosted
     version: "1.9.1"
   path_provider:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: path_provider
       sha256: "50c5dd5b6e1aaf6fb3a78b33f6aa3afca52bf903a8a5298f53101fdaee55bbcd"

pubspec.yaml

@@ -39,6 +39,9 @@ dependencies:
   audioplayers: ^6.7.1
   flutter_localizations:
     sdk: flutter
+  http: ^1.6.0
+  crypto: ^3.0.7
+  path_provider: ^2.1.5
 
 dev_dependencies:
   flutter_test:

test/data/remote/manifest_test.dart

@@ -0,0 +1,50 @@
+import 'package:block_seasons/data/remote/manifest.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  final json = {
+    'schemaVersion': 1,
+    'minAppBuild': 1,
+    'current': 'season_002',
+    'seasons': [
+      {
+        'seasonId': 'season_001',
+        'version': 1,
+        'packUrl': 'seasons/season_001/pack.json',
+        'sha256': 'abc123',
+      },
+      {
+        'seasonId': 'season_002',
+        'version': 3,
+        'packUrl': 'seasons/season_002/pack.json',
+        'sha256': 'def456',
+      },
+    ],
+  };
+
+  test('round-trips through json', () {
+    final manifest = RemoteManifest.fromJson(json);
+    expect(manifest.schemaVersion, 1);
+    expect(manifest.minAppBuild, 1);
+    expect(manifest.current, 'season_002');
+    expect(manifest.seasons, hasLength(2));
+    expect(manifest.seasons[1].seasonId, 'season_002');
+    expect(manifest.seasons[1].version, 3);
+    expect(manifest.seasons[1].packUrl, 'seasons/season_002/pack.json');
+    expect(manifest.seasons[1].sha256, 'def456');
+    expect(RemoteManifest.fromJson(manifest.toJson()).toJson(),
+        manifest.toJson());
+  });
+
+  test('rejects unsupported schema', () {
+    expect(
+      () => RemoteManifest.fromJson({...json, 'schemaVersion': 99}),
+      throwsFormatException,
+    );
+  });
+
+  test('missing current falls back to last season id', () {
+    final m = RemoteManifest.fromJson({...json}..remove('current'));
+    expect(m.current, 'season_002');
+  });
+}