Merge bitcoindevkit/bdk#1992: chore: add metadata fields to issue templates for triage

0eb852c75fcd72f5a919d21ab9645717319dfd97 chore: add metadata fields to issue templates for triage (Wei Chen)

Pull request description:

  ### Description

  This PR updates the GitHub issue templates `bug_report.md` and `enhancement_request.md` to improve triage and prioritization. Specifically, it adds structured fields for:

  * Production impact (e.g., blocking usage vs. nice-to-have)
  * Backend in use (Electrum, Esplora, RPC, etc.)
  * Project or organization (optional, helps identify high-priority users)

  The goal is to make it easier for maintainers to gauge the urgency and relevance of issues, especially for production users or high-impact integrations.

  ### Checklists

  #### All Submissions:

  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)

ACKs for top commit:
  evanlinjin:
    ACK 0eb852c75fcd72f5a919d21ab9645717319dfd97
  oleonardolima:
    ACK 0eb852c75fcd72f5a919d21ab9645717319dfd97

Tree-SHA512: 2b77a42a9cb79c2100c4fa22548990bad0413e573e7e7af86b4335bf752e3ffc0bf56ebcbb377aa599219a0c15baafcd7a61ede422bcaa56459f5bab8eb20a6b