Log in to the TreeTracker App using their Fabric certificates

## 🧑‍💼 Role
**User or Verifier**

## 📝 Description
As a user or verifier,
I want to log in using my Fabric certificate
So that I can securely access blockchain features.

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## ✅ Acceptance Criteria

- [ ] User presents their **Fabric certificate** for authentication
- [ ] System validates certificate and extracts the **role** from certificate attributes (e.g., `role=submitter` or `role=verifier`)
- [ ] A session is established either:
- Locally on the device
- Or via a secure backend service

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## 🔧 Sub-tasks

- [ ] Implement login UI that supports certificate-based authentication
- [ ] Integrate logic to parse, validate, and store Fabric certificate and key
- [ ] Establish session based on extracted role with appropriate access control

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## 📅 Sprint Info

| Attribute | Value |
|----------------|--------------------|
| **Sprint** | 2 |
| **Priority** | High |
| **Assignee** | Mobile App Dev |
| **Story Points**| 5 |

No source files, tests, or entry points are named. Start with the repository README and map the Android authentication flow before deciding where certificate handling and session setup belong. Done means the listed acceptance criteria are met for users and verifiers, including role extraction and access control.

Written by the indexing model from the issue text.