doc: Add a deployment guide covering Helm, containers and the PYPI

[641e16]

Summary

Adds a deployment guide for djehuty. Removes duplicate text elsewhere.

Changes

• docs/deployment.md: Add a guide for the three supported deployment methods, the prerequisites they share, the extra checks production mode enforces, and how to upgrade each one.
• mkdocs.yml: Add the deployment guide to the navigation.
• docs/index.md: Add the deployment guide to the documentation list.
• docs/introduction.md: Correct the Python requirement to 3.10, drop boto3 from the optional packages because it is a regular dependency, trim the remaining optional packages to a pointer, and replace the outdated container image table, which listed a devel tag that does not exist in GHCR, with a reference to the deployment guide.
• README.md: Replace the "Running in production" steps with a pointer to the deployment guide, removing instructions that led with the deprecated XML configuration format.

Approval Checklist

• I agree to follow Djehuty's code of conduct.
• I have read and I have follow the code contribution workflow.
• Code style and conventions were respected.
• Documentation has been updated where needed (README, docs, or examples).
• Review approved by at least one maintainer.
• Merge readiness (PR is squashed into a single commit and follows the commit template).

Issue Reference
Closes #233

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 18.06%. Comparing base (ea3ca20) to head (4e0a756).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #270   +/-   ##
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  Coverage   18.06%   18.06%           
=======================================
  Files          21       21           
  Lines       10507    10507           
  Branches     2038     2038           
=======================================
  Hits         1898     1898           
  Misses       8417     8417           
  Partials      192      192           

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