fix(web): preserve purchase context and pending action state

[cb8010d6]

Problem

Purchase collections and async action results could survive company/user changes, overwrite newer state, or clear a newer action's busy flag. Refresh after a completed write could erase another selected order's receipt draft, while a failed refresh obscured the successful save.

Changes

• Bind readable data/results to company, user and auth context version; hide stale collections immediately. Request generations reject A→B→A races and post-unmount callbacks; same-context token refresh remains valid.
• Share mutation guard with synchronous duplicate-submit lock and per-action identity; stale completion cannot unlock or overwrite a newer action.
• Preserve selection-specific invoice/receipt drafts; lock receipt inputs only for the selected order currently being received. Retain another order's edits across refresh when its authoritative quantities are unchanged.
• Show saved confirmation separately from refresh failure; stale data stays unavailable and read retry is explicit.
• Round remaining receipt defaults to four decimal places, including 0.3−0.1→0.2 compatibility with authoritative fix(purchase): prevent split and concurrent overreceipts #45 validation.
• Record iteration handoff, verified earlier heads and remaining production boundaries.

Validation

Luna max implementation with independent Astra review. Exact UI source commit a633f04:13 focused tests passed independently. Root integrated Web typecheck and all155 tests/27suites passed; integrated API704 tests passed. No new runtime dependencies or backend policy changes in this slice.

Exact integrated-head CI

Head f29c5b09c6f234474708df58ddf48940551d77bf: run 36289363016 passed every gate, including the aggregate validate check.

• 887 regular tests: 28 scripts + 704 API + 155 Web.
• 98 actual PostgreSQL regressions: includes 13 new receipt cases and eight new onboarding cases.
• 25 actual HTTP steps: 13 stocked-trade + 12 manufacturing, including real synthetic initializer, engineering-role login and release, BOM consumption, reversal and replay.
• 9 actual Chromium cases; browser identity/API responses are synthetic.
• Security audit, commitlint, Prisma/typecheck/lint/build gates passed. Shell and PowerShell restore command tests actually executed with zero root-test skips.
  Actual final-head job logs inspected; local integration tree exactly matches remote tree b7b9573a5856935b9be409f24ef9a02e5066caa1. This evidence supersedes pre-CI checkpoints in the committed handoff.

Stacked on #46; the review stack includes #43–#46. Restore tests simulate Docker and are not a real recovery drill. No production deployment/main merge or production-readiness claim; #35, operational recovery/sign-off and historical/accounting boundaries remain open.

[cb8010d6]

Base #46 now has exact-head all-green evidence: 4810b62, run36289249119; eight new onboarding PostgreSQL races actually passed (98 PG total), synthetic initializer and manufacturing login/release passed. This PR's own head f29c5b0 already passed 9 Chromium cases; full final-head CI is still running. Prior source-reviews and local155 Web/704 API results are not substituted for final CI.