refactor: Remove blockchain explorer

[YoshihitoAso]

📌 Description

This pull request removes all code and documentation related to the Blockchain Explorer feature from the project.

✅ Related Issues

• Close [FEATURE] Remove the BC Explorer feature #1748

🔄 Changes

Removal of Blockchain Explorer API and Models:

• Deleted the entire app/api/routers/bc_explorer.py file, removing all Blockchain Explorer API endpoints.
• Removed the IDXBlockData, IDXBlockDataBlockNumber, and IDXTxData database models.
• Removed Blockchain Explorer response and query schemas.

Configuration and Documentation Cleanup:

• Removed the Blockchain Explorer enable/disable setting from app/config.py.
• Removed the Blockchain Explorer section from the environment variable documentation in ENV_LIST.md.

Application and Build Process Updates:

• Removed inclusion of the Blockchain Explorer router from the FastAPI app in app/main.py.
• Removed the --extra ibet-explorer option from Python package installation commands.

📌 Checklist

• I have added tests where necessary.
• I have updated the documentation where necessary.

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
app
config.py	106	5	95%	62–63, 67, 120, 159
main.py	134	20	85%	107–108, 112, 117–119, 148–149, 191, 203–205, 216–218, 221, 225, 230, 234, 376
app/model/db
__init__.py	18	0	100%
app/model/schema
__init__.py	21	0	100%
TOTAL	46103	1560	96%

Tests	Skipped	Failures	Errors	Time
1504	0 💤	0 ❌	0 🔥	12m 9s ⏱️