Continue decimal.po translation - Add Context class and methods documentation

Translated entries covering:
- Context operations and constructor parameters
- Context management methods (clear_flags, clear_traps, copy)
- create_decimal and create_decimal_from_float methods
- Context arithmetic methods documentation
- Etiny and Etop functions
- localcontext function and usage examples

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: josix