Remove links & references to issues as that feature is now disabled in the repository. (And removing the now invalid discord invite)

[jcc10]

📝 Description

As it is now impossible to access issues for this repository, this is meant to remove references to requiring an open issue to preform pull-requests. It also removes recommendations for how to search the issues, and how to create new bug reports / issues.

Finally, it also removes the now invalid discord link.

Linked Issue: Fixes #-1 Because issues are disabled.

Required. Every PR must reference an approved issue. If no issue exists, open one and wait for maintainer approval before submitting a PR. Unsolicited PRs without a linked issue will be closed.

^^^: This can't be done because issues are disabled.

🏷️ Type of Change

• Bug fix
• New feature
• Enhancement to existing feature
• Refactor (no behavior change)
• Breaking change (existing functionality affected)
• Documentation update

🔧 Changes

• Modified CONTRIBUTING.md to remove references to issues and to remove the discord invite as it is now invalid.
• Modified .github/pull_request_template.md to remove reference indicating requirement to reference one or more issues, as issues are now defunct.

🧪 Testing (MANDATORY)

PRs without this section filled out will be closed. "Tests pass" or "Tested locally" is not sufficient. You must provide specifics.

Manual testing steps you performed:

1. This only changes 2 .md documentation files and does not alter any code.

Regression testing:

• This only changes 2 .md documentation files and does not alter any code.

Edge cases covered:

• This only changes 2 .md documentation files and does not alter any code.

Test output:

Backend test output (./gradlew test)

This only changes 2 `.md` documentation files and does not alter any code.

Frontend test output (ng test)

This only changes 2 `.md` documentation files and does not alter any code.

📸 Screen Recording / Screenshots (MANDATORY)

Every PR must include a screen recording or screenshots showing the change working end-to-end in a running local instance (both backend and frontend). This means you must have actually built, run, and tested the code yourself. PRs without visual proof will be closed without review.

Again, This only changes 2 `.md` documentation files and does not alter any code.

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✅ Pre-Submission Checklist

All boxes must be checked before requesting review. Incomplete PRs will be closed without review. No exceptions.

• This PR is linked to an approved issue
• Code follows project backend and frontend conventions
• Branch is up to date with develop (merge conflicts resolved)
• I ran the full stack locally (backend + frontend + database) and verified the change works
• Automated tests added or updated to cover changes (backend and frontend)
• All tests pass locally and output is pasted above
• Screen recording or screenshots are attached above proving the change works
• PR is a single focused change (one bug fix OR one feature, not multiple unrelated changes)
• PR is reasonably scoped (PRs over 1000+ changed lines will be closed, split into smaller PRs)
• No unsolicited refactors, cleanups, or "improvements" are bundled in
• Flyway migration versioning is correct (if schema was modified)
• Documentation PR submitted to booklore-docs (if user-facing changes)

🤖 AI-Assisted Contributions

If any part of this PR was generated or assisted by AI tools (Copilot, Claude, ChatGPT, etc.), all items below are mandatory. You are fully responsible for every line you submit. "The AI wrote it" is not an excuse, and AI-generated PRs that clearly haven't been reviewed are the #1 reason PRs get closed.

• I have read and understand every line of this PR and can explain any part of it during review
• I personally ran the code and verified it works (not just trusted the AI's output)
• PR is scoped to a single logical change, not a dump of everything the AI suggested
• Tests validate actual behavior, not just coverage (AI-generated tests often assert nothing meaningful)
• No dead code, placeholder comments, TODOs, or unused scaffolding left behind by AI
• I did not submit refactors, style changes, or "improvements" the AI suggested beyond the scope of the issue
• This issue was 100% Human written.

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💬 Additional Context (optional)

Again, This only changes 2 .md documentation files and does not alter any code.