Add FastAPI Backend and Core Models

[google-labs-jules]

Implemented a FastAPI backend to replace/augment the existing architecture.

• Defined 9 Core Models in Postgres (User, Lineage, Blueprint, etc.) using SQLModel.
• Implemented deterministic Inversion Engine and Resolver Service (mocked for Py3.12 compatibility).
• Added Stripe integration for Checkout and Webhooks.
• Created database schema in Supabase.
• Added backend tests.

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PR created automatically by Jules for task 2476157220298475531 started by @cjo93

[google-labs-jules]

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Project	Deployment	Actions	Updated (UTC)
thisisdefrag	Ready	Preview, Comment	Feb 5, 2026 7:20am
v0-thisisdefrag	Ready	Preview, Comment, Open in v0	Feb 5, 2026 7:20am