Description:

Modernize GitHub issue templates and PR template. The existing templates were outdated (still referenced "Embedchain"), had no auto-labeling, and the bug report was a single unstructured text
box. This PR:

• Rewrites bug report template with structured fields (component dropdown, env info, reproduction steps, expected vs actual) and labels: ["bug"] auto-labeling
• Rewrites feature request template with use case / proposed solution structure and labels: ["enhancement"] auto-labeling
• Creates new Benchmark Submission template with model config, results format, and labels: ["benchmark"] auto-labeling
• Updates documentation issue template with labels: ["documentation"] auto-labeling
• Updates config.yml contact links from Embedchain to Mem0 (Discord + Docs)
• Rewrites PR template with linked issue upfront, breaking changes section, test coverage checklist