chore: fix release workflow for renamed binary and removed Docker

[eshaffer321]

Summary

• Build from ./cmd/itemize/ — entry point moved from repo root when binary was renamed in chore: Rename binary and cmd directory from monarch-sync to itemize #16
• Output binary named itemize instead of monarchmoney-sync-backend
• Remove Docker job — Dockerfile was deleted in chore: Remove Dockerfile and Docker CI job #18, causing the job to always fail

Root cause

The release workflow wasn't updated alongside the renames in #16 and #18, so v0.1.0 failed with no Go files in /home/runner/work/itemize/itemize.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.41%. Comparing base (4d537e9) to head (3e29e06).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #22   +/-   ##
=======================================
  Coverage   56.41%   56.41%           
=======================================
  Files          43       43           
  Lines        4807     4807           
=======================================
  Hits         2712     2712           
  Misses       1931     1931           
  Partials      164      164           

Flag	Coverage Δ
unittests	56.41% <ø> (ø)

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