Add software architecture documentation with modular transformation design

[Copilot]

Adds comprehensive architecture documentation describing Flyover's four-stage modular transformation pipeline.

Changes

• docs/ARCHITECTURE.md: New architecture document covering:

  • High-level system diagram (Ingest → Triplify → Describe → Annotate)
  • Core component responsibilities and interfaces
  • Data flow through the pipeline
  • Extension points for new data sources, transformations, SPARQL templates, and ontology mappings
  • Directory structure and technology stack reference

• README.md: Added Architecture section linking to the new doc

Key Architectural Elements

┌─────────────┐    ┌─────────────┐    ┌─────────────┐    ┌─────────────┐
│   INGEST    │───▶│   TRIPLIFY  │───▶│  DESCRIBE   │───▶│  ANNOTATE   │
│   Module    │    │   Module    │    │   Module    │    │   Module    │
└─────────────┘    └─────────────┘    └─────────────┘    └─────────────┘

Extension points documented for:

• Adding new data sources (MySQL, Excel, etc.)
• Custom transformation steps
• SPARQL template patterns
• Ontology mapping schemas

Original prompt

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This section details on the original issue you should resolve

<issue_title>Draft an software architecture with modular transformation</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Draft an software architecture with modular transformation #68

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