Auto-scaling unit tests are #[ignore]d and never run in CI

[RUKAYAT-CODER]

Background

auto_scaling.rs (added to implement issue #322, automatic scaling for high-load scenarios) has three unit tests marked #[ignore]:

#[test]
#[ignore] // TODO: Fix test - requires proper contract context setup
fn test_batch_size_scaling() { ... }

#[test]
#[ignore] // TODO: Fix test - requires proper contract context setup
fn test_load_shedding_priority() { ... }

#[test]
#[ignore] // TODO: Fix test - requires proper contract context setup
fn test_gas_allocation_priority() { ... }

These tests already contain real assertions (batch size scaling under load, shedding priority, gas allocation priority) but are excluded from normal cargo test runs, so the auto-scaling logic that the system relies on under high load has no active regression coverage — a change that broke load shedding or batch sizing would not be caught.

Implementation Plan

• Determine the correct env.as_contract(...) / storage-initialization pattern needed so AutoScaler::initialize and subsequent calls run in a valid contract context inside these tests.
• Remove the #[ignore] attribute from each of the three tests once fixed.
• Extend test_load_shedding_priority to actually set up high-load metrics and assert low-priority operations are shed (the TODO comment in the test body notes this is currently missing).
• Confirm cargo test -p teachlink-contract auto_scaling --features testutils runs all three tests without --ignored.

Acceptance Criteria

• All three auto-scaling tests run by default (no #[ignore])
• test_load_shedding_priority asserts actual shedding behavior under high load, not just the critical-priority exemption
• cargo test passes with the tests enabled