docs: update rustdoc documentation for v0.5.0

[Berektassuly]

Comprehensive documentation update for docs.rs:

• lib.rs: Add overview, quick start, core concepts, common patterns, module structure, feature flags table, and serialization section
• parser.rs: Improve Parser trait and Platform enum docs with examples
• message.rs: Add field tables, construction examples, serialization info
• core/models.rs: Document OutputConfig with usage examples
• core/filter.rs: Add FilterConfig methods with_date_from/with_date_to/with_sender
• core/processor.rs: Document merge_consecutive with compression examples
• core/output/*.rs: Improve CSV/JSON/JSONL writer docs with format specs
• streaming/*.rs: Document StreamingParser, MessageIterator, StreamingConfig
• parsers/*.rs: Add platform-specific format details and examples

All doc-tests pass (cargo test --doc).

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/core/filter.rs	85.71%	2 Missing ⚠️

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