[Bug] Add dependency health check for poppler-utils

[BhakktiGautam]

📌 Closes Issue

Closes #329

🐛 Problem

When poppler-utils is missing on the host system, users see a cryptic 500 error after uploading a PDF. This provides no actionable feedback.

✅ Solution

Add a health check endpoint that validates system dependencies before users attempt conversions.

🚀 What's New?

Backend

• GET /health/dependencies - Returns status of all system dependencies
• GET /health - Simple health check

Frontend

• DependencyWarning component - Shows non-intrusive warning banner
• Auto-checks dependencies on page load
• Users see warnings before uploading files

📁 Files Added/Modified

New Files

File	Purpose
backend/utils/dependency_checker.py	Check poppler, tesseract, ghostscript
backend/blueprints/health.py	Health check endpoints
frontend/src/components/DependencyWarning.jsx	Warning banner UI

Modified Files

File	Change
backend/main.py	Register health blueprint
frontend/src/App.jsx	Add DependencyWarning component

🔧 API Response Example

{
  "status": "degraded",
  "dependencies": {
    "poppler-utils": {
      "installed": false,
      "required_for": ["PDF to PNG", "PDF to DOCX"],
      "install_command": "apt-get install poppler-utils",
      "brew_command": "brew install poppler",
      "windows_command": "conda install -c conda-forge poppler"
    },
    "tesseract-ocr": {
      "installed": true,
      "required_for": ["Image OCR"],
      "install_command": "apt-get install tesseract-ocr"
    },
    "ghostscript": {
      "installed": false,
      "required_for": ["PDF compression"],
      "optional": true,
      "install_command": "apt-get install ghostscript"
    }
  },
  "critical_missing": ["poppler-utils"]
}

Rule Compliance
No data storage

No external APIs

Pure file manipulation

🧪 How to Test
Backend
bash
curl http://localhost:5000/health/dependencies
Frontend
Start the app

See warning banner if poppler missing

Click close button to dismiss

##Checklist
/health/dependencies returns accurate status

Warning banner shows before upload

Works on Windows/Linux/Mac (commands for all OS)

Close button to dismiss banner

[vercel]

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[BhakktiGautam]

@Durgeshwar-AI

Following up on PR #337 (PDF Images Extractor).

Please review and add GSSoC label when possible.

Thanks! 🙏