Standardize shopping ingredients table naming

[MikeChristensen]

Summary

• make shoppingingredients the explicit canonical persistence table name
• rename the display-name index and align database-specific logs and comments
• document why database and domain terminology differ
• add NHibernate mapping regression coverage

Verification

• dotnet build: succeeded with zero warnings and errors
• dotnet test: 23 passed
• provisioned a fresh PostgreSQL database from the sample snapshot
• verified one shoppingingredients table, no ingredients table, the canonical index, nine referencing foreign keys, 2,707 ingredients, and 30 recipes