chore: add GitHub issue and pull request templates

.github/ISSUE_TEMPLATE/01_bug_report.md

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+---
+name: "Bug Report"
+about: Report a reproducible issue with swagger-codegen
+title: "[Bug]: "
+labels: Bug
+assignees: ''
+---
+
+## Description
+
+<!--
+Clearly describe the problem you're experiencing.
+
+Consider including:
+- What client/server/language are you generating?
+- What is the unexpected behavior?
+- What should have happened instead?
+-->
+
+## Swagger Codegen Version
+
+<!-- e.g. 3.0.45 -->
+
+## Language / Generator
+
+<!--
+Specify which generator you're using.
+Examples:
+- java
+- python
+- spring
+- typescript-angular
+- csharp-netcore
+-->
+
+## OpenAPI/Swagger Spec
+
+<!--
+Include a minimal example of the spec that reproduces the issue.
+Paste it inline (in triple backticks), or upload it as a gist.
+-->
+
+```yaml
+# example snippet or URL to full spec
+```
+## Command Line Used
+
+<!--
+Paste the full CLI command (or Maven/Gradle config) used to run codegen.
+-->
+
+```bash
+swagger-codegen generate -i petstore.yaml -l java -o output-folder
+```
+
+## Steps to Reproduce
+
+<!--
+Provide a clear, step-by-step list.
+
+1. ...
+2. ...
+3. ...
+-->
+
+## Expected Behavior
+
+<!--
+Describe what should have happened.
+-->
+
+## Actual Behavior
+
+<!--
+What actually happened? Include any errors, warnings, or incorrect output.
+-->
+
+## Related Issues / Repos
+
+<!--
+If this issue seems related to an existing one, mention it here.
+e.g. "Seems similar to #1234"
+-->
+
+## Environment
+
+- OS: <!-- e.g. Ubuntu 22.04, macOS 14, Windows 11 -->
+- Java Version: <!-- e.g. OpenJDK 17 -->
+- Build Tool: <!-- e.g. CLI, Maven, Gradle -->
+- Swagger Codegen CLI version: 
+
+## Additional Context
+
+<!--
+Include any links, files, screenshots, or notes that help clarify the problem.
+-->
+
+## Checklist
+
+- [ ] I have searched the [existing issues](https://github.com/swagger-api/swagger-codegen/issues) to make sure this is not a duplicate.
+- [ ] I have included a minimal and reproducible spec example.
+- [ ] I have explained how to reproduce the issue.
+- [ ] I have specified which generator/language is affected.

.github/ISSUE_TEMPLATE/02_question.md

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+---
+name: "Question"
+about: Ask a question about using swagger-codegen
+title: "[Question]: "
+labels: Question
+assignees: ''
+---
+
+## Question
+
+<!--
+Clearly describe your question or what you're trying to understand.
+
+To help us help you, consider including:
+- What generator/language are you using?
+- What are you trying to achieve?
+- Are you unsure about a CLI flag, config option, or spec feature?
+-->
+
+## Swagger Codegen Version
+
+<!-- e.g. 3.0.45 -->
+
+## Language / Generator
+
+<!--
+Specify the codegen target language or library.
+Examples:
+- java
+- spring
+- python
+- typescript-axios
+-->
+
+## OpenAPI/Swagger Spec
+
+<!--
+Optionally include a snippet of your spec, or describe its structure if relevant.
+-->
+
+## Command or Configuration Used
+
+<!--
+Paste the relevant CLI command or Maven/Gradle plugin configuration.
+-->
+
+```bash
+swagger-codegen generate -i your-spec.yaml -l typescript-axios -o output/
+```
+
+## What Have You Tried?
+
+<!--
+Describe any steps you’ve already taken to solve the issue or investigate the behavior.
+Examples:
+- I searched the documentation and examples
+- I looked through similar GitHub issues
+- I tried different config options or generators
+-->
+
+## Additional Details
+
+<!--
+Any extra context that might help:
+- links to documentation you consulted
+- screenshots
+- output logs or CLI behavior
+- clarification about the spec you're using
+-->
+
+## Checklist
+
+- [ ] I have searched the [existing issues](https://github.com/swagger-api/swagger-codegen/issues) and documentation.
+- [ ] I have provided enough context for maintainers to understand the question.
+- [ ] This is not a feature request or bug report.

.github/ISSUE_TEMPLATE/03_feature_request.md

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+---
+name: "Feature Request"
+about: Suggest an enhancement or new functionality for swagger-codegen
+title: "[Feature]: "
+labels: Feature
+assignees: ''
+---
+
+## Feature Description
+
+<!--
+Briefly describe the feature you'd like to see.
+
+Consider:
+- What problem does it solve?
+
+Examples:
+- Support for a new language or framework
+- Improvements to existing generator output
+- Additional CLI options or config settings
+
+-->
+
+## Use Case
+
+<!--
+Explain how this feature would be useful in real-world scenarios.
+Why is this feature important to you or your project?
+
+Try to answer:
+- What problem would this solve?
+- Is it blocking something you're trying to do?
+- How common is the use case?
+-->
+
+## Suggested Solution (optional)
+
+<!--
+Describe how you'd like to see this implemented.
+
+If applicable, include:
+- Example config options
+- Spec snippets
+- Expected output/code structure
+-->
+
+## Alternatives Considered
+
+<!--
+If you've tried workarounds or evaluated other solutions, describe them here.
+-->
+
+## Additional Context
+
+<!--
+Include any relevant information:
+- Related issues or discussions
+- Links to similar implementations
+- Screenshots or diagrams
+-->
+
+## Checklist
+
+- [ ] I have searched the [existing issues](https://github.com/swagger-api/swagger-codegen/issues) to make sure this feature hasn’t been requested already.
+- [ ] This feature would be useful to more than just my use case.
+- [ ] I have provided enough technical context to understand the request.