[P0 CRITICAL] Fix Reranking System Failure - Missing Template Parameter

[manavgup]

Problem

The reranking system is completely broken, causing the RAG to return irrelevant document chunks despite having 731 chunks from the IBM annual report containing revenue data.

Error: ValueError: Template is required for batch generation
Duration: 4.21 seconds wasted (23:52:44.939 → 23:52:49.155)
Impact: BLOCKING - No accurate retrieval without working reranking

Root Cause

backend/rag_solution/retrieval/reranker.py

The reranker calls generate_text() in batch mode but fails to pass the required template parameter.

Fix Strategy

1. Fetch RERANKING template from PromptTemplateService
2. Pass template to generate_text() for batch operations
3. Handle batch scoring properly

Success Criteria

• ✅ No ValueError: Template is required errors
• ✅ Reranking completes in <1 second
• ✅ Top 5-10 results have relevance scores >0.8
• ✅ Revenue-related chunks appear in top results

Files to Modify

• backend/rag_solution/retrieval/reranker.py (~20-30 LOC)

Related

• Part of Phase 0: Critical Blocking Fixes
• Reference: RAG_ISSUES.md Issue Add requirements.txt #1
• Timeline: Day 1