fix: update oracle tutorial for Pragma's v14 oracle deployment

[Keinberger]

Overview

This PR updates the "Consuming On-Chain Price Data from the Pragma Oracle"
tutorial so it works against Pragma's v14 oracle. Pragma recently redeployed
their Miden oracle for the v14 protocol, which changed both the deployment
addresses and the consumer-facing interface. The earlier v14 tutorial
migration (#186) only updated the SDK API surface, so the tutorial still
pointed at the dead pre-v14 deployment and failed at runtime.

Changes

• MASM (oracle_reader.masm) — get_price calls get_median with the
  v14 FPI ABI: 16 foreign-procedure inputs carrying the BTC/USD faucet pair
  (prefix 1, suffix 0), the new get_median procedure root, and the new
  oracle account ID.
• Rust (oracle_data_query.rs) — publishers are discovered from the
  oracle's pragma::oracle::publishers storage map (the old value-slot
  heuristic doesn't match the v14 layout), and each publisher's
  pragma::publisher::entries proof is requested keyed by the faucet-pair word.
• Docs (oracle_tutorial.md) — embedded code blocks synced to the runnable
  files; prose, addresses, and example output updated for the v14
  [is_tracked, median_price, amount] return layout.

Closes #200
Closes #113