chore: add Renovate dependency update config

[btotharye]

Adds Renovate bot configuration for automated dependency updates.

• Weekly PRs (Monday mornings)
• Auto-merge for patch updates
• Groups Python deps to reduce PR noise
• Major updates flagged for manual review

[Copilot]

Pull request overview

Adds a Renovate configuration to enable automated dependency update PRs for this repository, aligning with the project’s Python dependency management (PEP 621 + uv.lock) and reducing update noise.

Changes:

• Introduces renovate.json using config:recommended as a baseline.
• Configures a Monday-morning update schedule with PR rate limits and default dependency labeling.
• Adds package rules for patch auto-merge, grouping minor Python dependency updates, and labeling major updates for manual review.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.51%. Comparing base (4c44c17) to head (4cb5105).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #23   +/-   ##
=======================================
  Coverage   80.51%   80.51%           
=======================================
  Files           8        8           
  Lines         739      739           
=======================================
  Hits          595      595           
  Misses        144      144           

Flag	Coverage Δ
unittests	80.51% <ø> (ø)

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