fix(azure): M/L/N correctness fixes in providers/azure (scope, term, count, status, error-strings) #1055

Problem

This issue tracks remaining Medium/Low/Nit findings from the providers/azure code review (report 09) folded into PR #1045.

Findings: M1/M2 (appliedScopeType hardcoded + Scope dead field), M3 (ensureCapacityProviderRegistered swallows non-2xx status), M4 (inconsistent term parsing literal vs erroring parser), M5 (IsConfigured memoises error under sync.Once), M6 (no Count > 0 guard before purchase), L1 (non-deterministic price selection last-match-wins), L2 (parseReservationOrderID empty string not enforced at call site), L3 (merged service order enforced by comment only), L4 (Advisor pager break-on-error partial results as success), N1 (duplicate RetailPriceItem struct), N2 (error strings capitalized), N3 (contains alias for strings.Contains).

Source: docs/code-review/16-remaining-findings-plan.md FOLD-1045.

Fix: implemented as additional atomic commits on PR #1045 (branch fix/azure-pricing-httpclient).