docs: replace dead mainnet relay in v2 docs and CONTRIBUTING

[scarmuega]

The v2 docs and CONTRIBUTING.md still referenced
relays-new.cardano-mainnet.iohk.io:3001, which no longer resolves (NXDOMAIN).
Copy-pasted config snippets and oura watch commands using it fail to connect.

Swept it to the live backbone.mainnet.cardanofoundation.org:3001 relay,
matching the example configs fixed in #939. Hostname-only change.

The v1 docs are maintained on the lts/v1 branch and are fixed in a separate PR
targeting that branch.

🤖 Generated with Claude Code

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📝 Walkthrough

Walkthrough

All documentation files and the contributing guide replace the Cardano mainnet relay endpoint relays-new.cardano-mainnet.iohk.io:3001 with backbone.mainnet.cardanofoundation.org:3001. The change spans 11 files across v1 and v2 docs with no logic or behavior modifications.

Changes

Mainnet Relay Endpoint Update

Layer / File(s)	Summary
Contributing guide and v1 docs .github/CONTRIBUTING.md, docs/v1/advanced/rollback_buffer.mdx, docs/v1/installation/docker.mdx, docs/v1/sources/n2n.mdx, docs/v1/usage/daemon.mdx, docs/v1/usage/dump.mdx, docs/v1/usage/watch.mdx	Replaces all occurrences of the old IOHK relay hostname with backbone.mainnet.cardanofoundation.org:3001 in example configurations and command snippets across the contributing guide and all v1 documentation pages.
v2 docs docs/v2/sources/n2n.mdx, docs/v2/usage/daemon.mdx, docs/v2/usage/dump.mdx, docs/v2/usage/watch.mdx	Replaces the same old relay hostname with backbone.mainnet.cardanofoundation.org:3001 in all v2 documentation example configurations and command snippets, including the public relays listing in the N2N source page.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Suggested reviewers

• paulobressan

Poem

🐇 Hop, hop, the old relay's gone away,
A new backbone has come to stay!
Cardano Foundation holds the line,
At port three-thousand-and-one so fine.
The docs all sparkle, fresh and bright—
Every example updated right! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: replacing a dead mainnet relay endpoint across documentation and CONTRIBUTING.md.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/docs-dead-relay

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Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

docs/v1/sources/n2n.mdx (1)

56-63: ⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

Keep the testnet example on a testnet relay.

This block is labeled testnet, but it now points at the mainnet backbone endpoint, so copying it with magic = "testnet" will not work. As shown by src/sources/n2n.rs, the configured peer string is used verbatim at connect time.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@docs/v1/sources/n2n.mdx` around lines 56 - 63, The testnet example in the N2N
configuration block contains an inconsistency: the address field points to the
mainnet backbone endpoint (backbone.mainnet.cardanofoundation.org:3001) while
the magic field specifies testnet. This mismatch will cause connection failures
since the peer string is used verbatim at connect time. Update the address field
in the toml code block to point to an actual testnet relay endpoint instead of
the mainnet backbone, ensuring the configuration matches the testnet magic
value.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@docs/v1/sources/n2n.mdx`:
- Around line 56-63: The testnet example in the N2N configuration block contains
an inconsistency: the address field points to the mainnet backbone endpoint
(backbone.mainnet.cardanofoundation.org:3001) while the magic field specifies
testnet. This mismatch will cause connection failures since the peer string is
used verbatim at connect time. Update the address field in the toml code block
to point to an actual testnet relay endpoint instead of the mainnet backbone,
ensuring the configuration matches the testnet magic value.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c6bb1b3f-8872-40c2-8dbc-69d526b8780b

📥 Commits

Reviewing files that changed from the base of the PR and between 44da48e and 0c697b1.

📒 Files selected for processing (11)

• .github/CONTRIBUTING.md
• docs/v1/advanced/rollback_buffer.mdx
• docs/v1/installation/docker.mdx
• docs/v1/sources/n2n.mdx
• docs/v1/usage/daemon.mdx
• docs/v1/usage/dump.mdx
• docs/v1/usage/watch.mdx
• docs/v2/sources/n2n.mdx
• docs/v2/usage/daemon.mdx
• docs/v2/usage/dump.mdx
• docs/v2/usage/watch.mdx