- Add rust_decimal feature to sqlx and tiberius for proper Decimal type handling
- Fix try_get_unchecked<String> causing NULL or garbled output for numeric types
- Add numeric_precision and numeric_scale to ColumnInfo for all database drivers
- Update frontend to display precision (e.g., numeric(20,6)) in column headers
- Fix typeColorClass to handle type names with precision suffix
Root cause: PostgreSQL binary protocol sends NUMERIC as PgNumeric binary format,
not UTF-8 text. try_get_unchecked<String> attempted to decode binary bytes as UTF-8,
causing decode failures (NULL) or garbage characters (乱码).
- Add comment field to ColumnInfo (MySQL COLUMN_COMMENT, PostgreSQL col_description)
- Show column comments in sidebar tree nodes
- Show column comments on hover in data grid header
- Default MySQL charset to utf8mb4 for proper CJK support
Closes#14
t8y2