FEATURE REQUEST:[Feature Request / GSoC Proposal] Energy-Based Task Matching & Single-Task Focus Mode (PulseSync Concept)

### Is your feature request related to a problem?

- [x] Yes, it is related to a problem

### Describe the feature you'd like

### 💡 Overview & Motivation
To enhance **Ell-ena's** smart productivity ecosystem, I propose integrating an **Energy-Based Task Matching Engine** alongside a **Single-Task Focus Mode** (inspired by the *PulseSync* design concept).

Instead of forcing users through dense task lists during low-energy states, Ell-ena will dynamically evaluate task complexity using its AI capabilities and match tasks with the user's current cognitive state (**High**, **Medium**, or **Calm**), helping mitigate task paralysis.

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### 🚀 Proposed Integration Architecture

#### 1. Energy Matcher (Gemini NLU & RAG Filtering)
* **Location:** `lib/services/ai_service.dart` & `lib/screens/tasks/`
* **Functionality:** Extend the Gemini NLU pipeline to categorize task difficulty/cognitive load. When a user selects their energy state, the system filters and suggests tasks optimized for their current bandwidth.

#### 2. Single-Task Focus Mode
* **Location:** `lib/screens/tasks/`
* **Functionality:** A distraction-free Flutter view displaying **only one task at a time**, temporarily hiding complex project structures and navigation drawers to promote immediate action.

#### 3. Modern Soft Pastel Theme & Micro-Interactions
* **Location:** `lib/widgets/custom_widgets.dart` & `lib/screens/tasks/`
* **Functionality:** Introduce a calm Pastel Design System option (super-rounded components, gentle gradients) along with lightweight achievement feedback (e.g., Lottie confetti burst + dynamic AI encouragement quotes upon completion).

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### 🛠️ Proposed Implementation Steps
- [ ] Implement the Energy Selection UI state inside `lib/screens/onboarding/` or task dashboard.
- [ ] Extend `ai_service.dart` with Gemini prompts to rank/filter tasks by cognitive load.
- [ ] Build the Single-Task Focus Mode component in `lib/screens/tasks/`.
- [ ] Add custom pastel theme tokens and completion micro-animations to `lib/widgets/custom_widgets.dart`.

### Record

- [x] I agree to follow this project's Code of Conduct
- [x] I want to work on implementing this feature

Start by reading lib/services/ai_service.dart and the task, onboarding, and widget paths named in the proposal to understand the existing task flow and Gemini integration. Done would require an agreed scope covering energy selection and matching, single-task focus mode, pastel theme tokens, and completion micro-interactions; the issue does not identify tests or a narrower entry point.

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