Add comprehensive project documentation

- Add detailed implementation plan (main-plan.md)
- Add professional README with project overview
- Include original specifications and screenshots
- Document technology stack and architecture
- Provide setup and deployment instructions

original/project2.md

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+# Znakovni.hr – Full Application Replication Specification
+
+## Purpose
+This document specifies the **exact functionality, structure, and behavior** of the Znakovni.hr web application.
+The goal is to enable AI programming agents to design and implement a **functionally identical copy** of the platform,
+including UX flows, features, and system architecture.
+
+Explicit permission has been granted by the original author to replicate the application for demonstration,
+research, and AI capability showcasing purposes.
+
+---
+
+## 1. Application Overview
+
+Znakovni.hr is a **web-based Croatian Sign Language (HZJ) platform** that provides:
+- A video-based sign language dictionary
+- Sentence construction tools using signs
+- Video sentence playback
+- User accounts and cloud storage
+
+The platform functions as a **learning tool, reference dictionary, and sentence composition environment**.
+
+---
+
+## 2. Main Navigation & Screens
+
+### 2.1 Sidebar Navigation
+Persistent left sidebar with the following items:
+
+- Početna (Home)
+- Riječi (Dictionary)
+- Znakopis (Sentence Builder)
+- Video rečenica (Video Sentence Player)
+- Oblak (Cloud Documents)
+- Korištenje aplikacije (Help)
+- Zajednica (Community)
+- Komentari (Comments)
+- Prijavi grešku (Bug Report)
+- Sign in / Sign out
+
+Sidebar is visible on all authenticated pages.
+
+---
+
+## 3. Screens & Functionality
+
+### 3.1 Home (Početna)
+- Intro headline: “Tvoj put u svijet znakovnog jezika”
+- Feature overview cards:
+  - Dictionary
+  - Sentence composition (Znakopis)
+  - Video sentences
+  - Cloud documents
+
+Static informational screen.
+
+---
+
+### 3.2 Dictionary (Riječi)
+
+#### Features
+- Free-text search
+- Filters:
+  - Word type
+  - CEFR level (A1–C2)
+- Paginated grid of word cards
+
+#### Word Card
+Each card includes:
+- Icon representation
+- Word label
+- Difficulty color indicator
+- Actions:
+  - Add to sentence
+  - Info
+
+#### Word Detail
+- Embedded sign video
+- Linguistic metadata
+- Usage context
+
+---
+
+### 3.3 Znakopis (Sentence Builder)
+
+#### Purpose
+Visual assembly of sign-language sentences.
+
+#### Layout
+- Sentence structure panel (left)
+- Sentence description editor (right)
+
+#### Features
+- Add words from dictionary
+- Reorder via drag or controls
+- Remove words
+- Multi-page sentence support
+- Save as document
+
+Documents may be saved locally or in cloud.
+
+---
+
+### 3.4 Video Rečenica (Video Sentence)
+
+#### Purpose
+Playback of complete sentences using video signs.
+
+#### Layout
+- Video player (left)
+- Sentence structure view (right)
+
+#### Controls
+- Play / Pause
+- Step navigation
+- Repeat
+- Speed adjustment (optional)
+
+---
+
+### 3.5 Oblak (Cloud Documents)
+
+#### Purpose
+Centralized storage of sentence documents.
+
+#### Features
+- Upload documents
+- Save Znakopis documents
+- Load and edit documents
+- Document listing
+
+---
+
+### 3.6 Authentication
+
+#### Login Methods
+- Email/password
+- Google OAuth
+- Microsoft OAuth
+
+#### Authenticated Capabilities
+- Document persistence
+- User-specific content
+- Session continuity
+
+---
+
+## 4. Core Data Models
+
+### User
+- id
+- email
+- display_name
+- auth_provider
+- created_at
+
+### Word
+- id
+- text
+- word_type
+- cefr_level
+- icon_url
+- video_url
+
+### Sentence
+- id
+- user_id
+- title
+- created_at
+
+### SentenceItem
+- id
+- sentence_id
+- word_id
+- position
+
+### Document
+- id
+- user_id
+- sentence_id
+- storage_location
+- updated_at
+
+---
+
+## 5. API Surface (Illustrative)
+
+- GET /api/words
+- GET /api/words/{id}
+- POST /api/sentences
+- PUT /api/sentences/{id}
+- GET /api/documents
+- POST /api/auth/login
+
+---
+
+## 6. Video Handling
+
+- Short video clips per word
+- Consistent framing
+- Loop-ready
+- Neutral background
+
+Sentence playback = sequential video concatenation.
+
+---
+
+## 7. Non-Functional Requirements
+
+- Desktop-first responsive UI
+- High accessibility
+- Fast filtering/search
+- Stateless backend
+- Secure auth
+
+---
+
+## 8. Architecture (Technology-Agnostic)
+
+- SPA frontend
+- REST backend
+- Relational database
+- Object storage for videos
+- OAuth + JWT authentication
+
+---
+
+## 9. Functional Parity Criteria
+
+- Dictionary search and filters
+- Sentence creation
+- Video sentence playback
+- Cloud document storage
+- Authentication
+
+---
+
+## 10. Scope
+
+This document defines a **1:1 functional replication** of the Znakovni.hr application,
+intended for controlled demonstration and AI-driven implementation planning.