Enable manual dispatch for build workflow

[Copilot]

This PR adds manual run support to the existing reusable build workflow in nervosnetwork/ckb-explorer. The change is scoped to workflow triggers only and preserves current workflow_call behavior, inputs/outputs, and secrets contract.

• Trigger configuration

  • Added workflow_dispatch under on: in .github/workflows/build.yml.
  • Kept existing workflow_call block unchanged (including secrets and outputs).

• Change scope

  • Single-file, minimal YAML update with no job/step logic changes.

on:
  workflow_dispatch:
  workflow_call:
    secrets:
      GHCR_USERNAME:
        required: true
      GHCR_TOKEN:
        required: true

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (f373f6b) to head (febc8e5).
⚠️ Report is 978 commits behind head on develop.

❌ Your project status has failed because the head coverage (0.00%) is below the target coverage (90.00%). You can increase the head coverage or adjust the target coverage.

❗ There is a different number of reports uploaded between BASE (f373f6b) and HEAD (febc8e5). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (f373f6b)	HEAD (febc8e5)
	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #2944       +/-   ##
===========================================
- Coverage    67.56%   0.00%   -67.57%     
===========================================
  Files          289     292        +3     
  Lines         7944   14385     +6441     
===========================================
- Hits          5367       0     -5367     
- Misses        2577   14385    +11808     

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