Restructure backend package layout

[ahmedmmordi]

Related to #60, as we move toward decoupling the frontend, having a well-structured backend makes it easier to identify and expose clean API boundaries.

The web/ package has become a catch-all. It mixes REST endpoints, business services, infrastructure wiring, and utilities in one flat directory, making the codebase harder to navigate and reason about.

Proposed structure

ai/mnemosyne_systems/
├── model/       unchanged
├── resource/    all *Resource.java files
├── service/     PdfService, ...
├── util/        AuthHelper, ...
├── infra/       GlobalExceptionMapper, ...
└── init/        AppSeeder

What this is not

Purely a package reorganization. No logic changes, no renamed classes, only import statements and directory structure.

Questions

• Does this proposal make sense, or is it something we can live with for now and revisit over time?
• Any naming preferences? (util/ vs helper/, infra/ vs config/)

[jesperpedersen]

@ahmedmmordi No, the above looks good