docs: reorganize prompt evaluation guides in navigation (#2346)

## Issue Link / Problem Description
- Issue: The `iterate_prompt.md` guide was incorrectly placed under
Customizations → General, when it actually demonstrates a complete
application workflow for evaluating and improving prompts.
- The navigation structure didn't logically group related prompt
evaluation guides together.

## Changes Made
- Moved `iterate_prompt.md` from `docs/howtos/customizations/` to
`docs/howtos/applications/`
- Created new "Prompt Evaluation" subsection under Applications in
`mkdocs.yml`
- Grouped both prompt evaluation guides together:
  - Iterate and Improve Prompts
  - Systematic Prompt Optimization
- Updated `docs/howtos/applications/index.md` with the new Prompt
Evaluation section
- Removed misplaced entries from the Customizations section in
`mkdocs.yml`
- Fixed broken link (missing .md extension) for prompt_optimization in
applications/index.md

## Testing
### How to Test
- [x] Automated tests added/updated: Pre-commit hooks passed (formatting
checks)
- [x] Manual testing steps:
  1. Build the documentation locally: `make build-docs`
2. Verify navigation structure shows "Prompt Evaluation" under
Applications
  3. Confirm both guides are accessible and properly linked
  4. Verify no broken links in the navigation

Author: sanjeed5

docs/howtos/applications/index.md

@@ -4,19 +4,24 @@ Ragas in action. Examples of how to use Ragas in various applications and
 usecases to solve problems you might encounter when you're building.
 
 
+## Prompt Evaluation
+
+- [Iterate and Improve Prompts](iterate_prompt.md)
+- [Systematic Prompt Optimization](prompt_optimization.md)
+
 ## Metrics
 
 - [Debug LLM based metrics using tracing](_metrics_llm_calls.md)
 - [Evaluating Multi-turn Conversations](evaluating_multi_turn_conversations.md)
 - [Estimate cost of evaluation](_cost.md)
 - [Evaluations with Vertex AI models](vertexai_x_ragas.md)
-- [Systematic Approach for Prompt Optimization](prompt_optimization)
 
-## Testset Generation:
+## Testset Generation
 
 - [Single-hop Query Testset](singlehop_testset_gen.md)
 
 ## Benchmarking
+
 - [Evaluate a New LLM For Your Use Case](benchmark_llm.md)
 
 ## RAG Evaluation

docs/howtos/customizations/iterate_prompt.md renamed to docs/howtos/applications/iterate_prompt.md

@@ -95,14 +95,12 @@ nav:
               - Run Config: howtos/customizations/_run_config.md
               - Caching: howtos/customizations/_caching.md
               - Cancelling Tasks: howtos/customizations/cancellation.md
-              - Iterate Prompts: howtos/customizations/iterate_prompt.md
           - Metrics:
               - Modify Prompts: howtos/customizations/metrics/_modifying-prompts-metrics.md
               - Adapt Metrics to Languages: howtos/customizations/metrics/_metrics_language_adaptation.md
               - Write your own Metrics: howtos/customizations/metrics/_write_your_own_metric.md
               - Write your own Metrics - (advanced): howtos/customizations/metrics/_write_your_own_metric_advanced.md
               - Train and Align Metrics: howtos/customizations/metrics/train_your_own_metric.md
-              - Systematic Approach for Prompt Optimization: howtos/applications/prompt_optimization.md
           - Testset Generation:
               - Non-English Testset Generation: howtos/customizations/testgenerator/_language_adaptation.md
               - Persona Generation: howtos/customizations/testgenerator/_persona_generator.md
@@ -111,6 +109,9 @@ nav:
 
       - Applications:
           - howtos/applications/index.md
+          - Prompt Evaluation:
+            - Iterate and Improve Prompts: howtos/applications/iterate_prompt.md
+            - Systematic Prompt Optimization: howtos/applications/prompt_optimization.md
           - Metrics:
             - Cost Analysis: howtos/applications/_cost.md
             - Evaluating Multi-turn Conversations: howtos/applications/evaluating_multi_turn_conversations.md