feat: Implement startup retry mechanism for custom stations and equalizer persistence

- Added state management for startup retry and custom station handling in `EstadoRadio`.
- Created tasks for implementing strict TDD with RED tests for HTTP failure retries and EQ persistence.
- Developed verification report to ensure compliance with TDD practices.
- Introduced fake services for testing, including `FakeServicioAudio`, `FakeServicioFavoritos`, and `FakeServicioRadio`.
- Implemented widget tests for `PantallaInicio` and `PantallaFavoritos` to validate UI behavior with custom stations.
- Enhanced `ServicioRadio` to support host rotation and retry logic for API calls.
- Established a new configuration file to enforce project constraints and testing rules.

openspec/config.yaml

@@ -0,0 +1,64 @@
+schema: spec-driven
+
+context: |
+  Tech stack: Flutter/Dart app for Android+iOS.
+  Architecture: Provider/ChangeNotifier with Spanish domain folders: estado, modelos, pantallas, servicios, widgets.
+  Testing: flutter_test via `flutter test`; Strict TDD enabled.
+  Style: flutter_lints via analysis_options.yaml; use flutter analyze and dart format.
+  Constraint: never run flutter build after changes.
+
+strict_tdd: true
+
+testing:
+  strict_tdd: true
+  detected: 2026-04-27
+  test_runner:
+    framework: flutter_test
+    command: flutter test
+  layers:
+    unit:
+      available: true
+      tool: flutter_test
+    integration:
+      available: false
+      tool: null
+    e2e:
+      available: false
+      tool: null
+  coverage:
+    available: true
+    command: flutter test --coverage
+  quality_tools:
+    linter:
+      available: true
+      command: flutter analyze
+    type_checker:
+      available: true
+      command: flutter analyze
+    formatter:
+      available: true
+      command: dart format .
+
+rules:
+  proposal:
+    - Include rollback plan for risky changes
+    - Identify affected modules/packages
+  specs:
+    - Use Given/When/Then format for scenarios
+    - Use RFC 2119 keywords
+  design:
+    - Include architecture decisions with rationale
+  tasks:
+    - Group tasks by phase
+    - Use hierarchical numbering
+    - Keep tasks small enough to complete in one session
+  apply:
+    - Follow existing code patterns and conventions
+    - Strict TDD Mode is active
+    - Never run flutter build
+  verify:
+    - Run tests if possible
+    - Compare implementation against every spec scenario
+    - Never run flutter build
+  archive:
+    - Persist final state to Engram and openspec