docs: add six-page final project report

[Tech-Matt]

Summary

Adds the exam project report for Mattia Rizzo and Alan Masutti:

• report/RizzoMasutti_Report.pdf: the compiled, self-contained six-page A4 report;
• the four-file LaTeX source structure from the official course template;
• concise local compilation instructions;
• a repository README link to the report.

The report keeps the template's original margins and default article font size. It covers the actor architecture, update storage, timeout management, controlled crashes, ring election, election termination, synchronization, assumptions, validation, and the requested AI-use declaration.

Sequential-consistency coverage

Sequential consistency is a central argument in Section 2.2, not only a stated outcome. The report explains:

1. how the client FIFO queue preserves program order;
2. how the coordinator assigns a unique immutable EpochPair in mailbox order;
3. why coordinator-to-replica and replica-to-coordinator FIFO channels make quorum causality preserve update order;
4. why replicas apply only matching WRITEOK messages and therefore hold prefixes of the same total order;
5. why a successful write followed by a read from the same client/replica observes that write or a later ordered value;
6. how election selects the longest applied prefix and synchronization establishes the next epoch's common baseline.

The report also states the additional assumption of the current snapshot-based interrupted-WRITEOK recovery instead of overclaiming the strongest uniform-agreement case.

Validation

• Tectonic compilation: successful;
• output: exactly 6 A4 pages;
• visual inspection: all six pages checked;
• LaTeX: no overfull text, undefined references, or compilation errors;
• required authors: Mattia Rizzo and Alan Masutti;
• AI clause: included in Section 3.5;
• Gradle test: successful on the unchanged implementation;
• staged diff check: clean.

Review note

This is intentionally a draft PR for detailed document review.

It is stacked on #99 (fix/sequential-consistency) because the report describes that implementation. Using the feature branch as the base keeps this PR's diff limited to report files. After #99 is accepted, this PR can be merged into that branch or retargeted to main.