docs: remove IPFS deps from local setup section

[ham-76]

the codebase no longer depends on a running/self-hosted IPFS node. Instead, it uses two third-party hosted IPFS services:

1. Storacha (web3.storage) — via the @web3-storage/w3up-client SDK. It authenticates with a private key + delegation proof (fetched from S3) and calls uploadDirectory to pin content.
2. Pinata — via the pinata-web3 SDK. After uploading to Storacha, it pins the same CID on Pinata for redundancy using pinata.upload.cid(...).

Both are cloud-hosted IPFS pinning services accessed through their respective SDKs/APIs. The relevant env vars are:
• MATTERS_STORACHA_PROOF_S3_BUCKET, MATTERS_STORACHA_PROOF_S3_KEY, MATTERS_STORACHA_PRIVATE_KEY — for Storacha
• MATTERS_PINATA_JWT, MATTERS_PINATA_GATEWAY, MATTERS_PINATA_GROUP_ID — for Pinata

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.66%. Comparing base (308ea14) to head (23f8916).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4755   +/-   ##
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  Coverage    57.66%   57.66%           
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  Files         1007     1007           
  Lines        19817    19817           
  Branches      4153     4153           
========================================
  Hits         11427    11427           
  Misses        8330     8330           
  Partials        60       60           

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