Establish project foundation with clean architecture and core infrastructure

[Copilot]

Sets up "Second Brain" Flutter app foundation: clean architecture structure, core dependencies, CI/CD, and base implementation. Enables immediate development on Phase 1 (Notes CRUD).

Architecture & Structure

• Clean Architecture with feature-based modules (notes, chat, search, voice)
• Three-layer separation per feature: data/, domain/, presentation/
• Core infrastructure: constants/, errors/, theme/, utils/
• .gitkeep files maintain empty directories in git (20 total)

Dependencies

State Management: Riverpod 2.6.1 with annotations and code generation
Database: Isar 4.0.0-dev.14 (local-first NoSQL with future pgvector sync)
UI: Material 3 theme, google_fonts, flutter_svg
Utils: uuid, intl, path_provider

Core Implementation

Theme: Material 3 with purple/indigo brain palette (#6B4EFF primary), light/dark modes

Error Handling: Base Failure class with ServerFailure, CacheFailure, GeneralFailure

Extensions:

'hello'.capitalize()           // "Hello"
DateTime.now().timeAgo         // "2 hours ago"
DateTime.now().formatted       // "Feb 11, 2026"

App Structure:

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(const ProviderScope(child: App()));
}

CI/CD

GitHub Actions workflow with Flutter 3.38.4 stable:

• flutter pub get → dart format --check → flutter analyze → flutter test
• Triggers on push/PR to main

Documentation

• README: 155 lines with architecture diagram, tech stack, 6-phase roadmap
• ADR 001: Hybrid (local-first + cloud sync) architecture decision with rationale

App Constants

AppConstants.appName     // "Second Brain"
AppConstants.appVersion  // "0.1.0"
AppConstants.dbName      // "second_brain_db"

Placeholder home screen renders with brain icon and Material 3 theming. Tests updated for new structure.

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• canonical-bos01.cdn.snapcraftcontent.com
  • Triggering command: /usr/lib/snapd/snapd /usr/lib/snapd/snapd --print-foreign-architectures (dns block)
• google.com
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• https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_3.24.0-stable.tar.xz
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• https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_3.38.4-stable.tar.xz
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Original prompt

Overview

Set up the complete project foundation for "Second Brain" — a RAG-Powered Note Taking App built with Flutter. This PR should establish clean architecture, add core dependencies, set up CI/CD, and create a professional README.

Project Context

• App: Second Brain — a local-first notes app where you can "chat" with your notes using AI
• Tech Stack: Flutter, Riverpod, Isar DB, LangChain.dart, Google Gemini API, Supabase (pgvector)
• Architecture: Clean Architecture + MVVM with feature-based folder structure
• Project path: D:\second_brain
• Flutter version: 3.38.4 (stable channel)
• Dart version: 3.10.3

Tasks

1. 📁 Clean Architecture Folder Structure

Create the following folder structure with placeholder .gitkeep files so folders are tracked by Git:

lib/
├── app.dart                         # App widget with MaterialApp, theme, routing
├── main.dart                        # Entry point — initialize providers, run app (update existing)
├── core/
│   ├── constants/
│   │   └── app_constants.dart       # App-wide constants (app name, version, etc.)
│   ├── errors/
│   │   └── failures.dart            # Base Failure class for error handling
│   ├── theme/
│   │   └── app_theme.dart           # Light and dark theme definitions
│   └── utils/
│       └── extensions.dart          # Useful Dart extensions (String, DateTime, etc.)
├── features/
│   ├── notes/
│   │   ├── data/
│   │   │   ├── datasources/
│   │   │   │   └── .gitkeep
│   │   │   ├── models/
│   │   │   │   └── .gitkeep
│   │   │   └── repositories/
│   │   │       └── .gitkeep
│   │   ├── domain/
│   │   │   ├── entities/
│   │   │   │   └── .gitkeep
│   │   │   ├── repositories/
│   │   │   │   └── .gitkeep
│   │   │   └── usecases/
│   │   │       └── .gitkeep
│   │   └── presentation/
│   │       ├── providers/
│   │       │   └── .gitkeep
│   │       ├── screens/
│   │       │   └── .gitkeep
│   │       └── widgets/
│   │           └── .gitkeep
│   ├── chat/
│   │   ├── data/
│   │   │   └── .gitkeep
│   │   ├── domain/
│   │   │   └── .gitkeep
│   │   └── presentation/
│   │       └── .gitkeep
│   ├── search/
│   │   ├── data/
│   │   │   └── .gitkeep
│   │   ├── domain/
│   │   │   └── .gitkeep
│   │   └── presentation/
│   │       └── .gitkeep
│   └── voice/
│       ├── data/
│       │   └── .gitkeep
│       ├── domain/
│       │   └── .gitkeep
│       └── presentation/
│           └── .gitkeep
└── shared/
    ├── widgets/
    │   └── .gitkeep
    └── providers/
        └── .gitkeep

2. 📦 Core Dependencies in pubspec.yaml

Add these dependencies to the existing pubspec.yaml:

Dependencies:

dependencies:
  flutter:
    sdk: flutter
  # State Management
  flutter_riverpod: ^2.6.1
  riverpod_annotation: ^2.6.1
  
  # Local Database
  isar: ^4.0.0-dev.14
  isar_flutter_libs: ^4.0.0-dev.14
  
  # UI
  google_fonts: ^6.2.1
  flutter_svg: ^2.0.17
  
  # Utilities
  uuid: ^4.5.1
  intl: ^0.19.0
  path_provider: ^2.1.5
  
dev_dependencies:
  flutter_test:
    sdk: flutter
  flutter_lints: ^5.0.0
  
  # Code Generation
  riverpod_generator: ^2.6.3
  build_runner: ^2.4.14
  isar_generator: ^4.0.0-dev.14

3. ⚙️ GitHub Actions CI/CD

Create .github/workflows/ci.yml:

• Trigger on push and PR to main
• Run flutter pub get
• Run flutter analyze
• Run flutter test
• Use Flutter 3.38.4 stable

4. 📝 Professional README

Replace the existing README.md with a professional one that includes:

• App name with emoji: 🧠 Second Brain
• Short description: "RAG-Powered Note Taking App — Chat with your notes using AI"
• Badges: Flutter, Dart, License MIT, CI status
• Features section (planned): Notes CRUD, Semantic Search, RAG Chat, Voice-to-Note, Cloud Sync
• Tech stack table: Flutter, Riverpod, Isar, LangChain.dart, Gemini API, Supabase
• Architecture section: Clean Architecture + MVVM explanation with folder structure
• Getting Started section: Prerequisites, Installation, Running
• Roadmap section with phases:
  • Phase 1: Foundation (Notes CRUD) ⬅️ Current
  • Phase 2: Intelligence Layer (Embeddings + Vector Search)
  • Phase 3: RAG Chat (LangChain.dart + Gemini)
  • Phase 4: Cloud Sync (Supabase + pgvector)
  • Phase 5: Voice-to-Note
  • Phase 6: Polish & Ship
• License: MIT
• Author: Muhammad-Bilal-03

5. 📋 Architecture Decision Record

Create ADR/001-hybrid-architecture.md:

• Title: Use Hybrid (Local-First + Cloud Sync) Architecture
• Status: Accepted
• Context: Why hybrid over pure local or pure cloud
• Decision: Local-first with Isar DB + optional Supabase sync
• Consequences: More complex but better UX, offline support, and skill demonstration

6. 🎨 App Theme & Base Structure

Create actual Dart files with real code:

lib/core/theme/app_theme.dart — Define light and dark themes using Material 3 with a custom color scheme (use a brain/purple theme — primary color around purple/indigo).

lib/core/constants/app_constants.dart — App name: "Second...

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