feat: cut over canonical Meta commerce tracking

[Mar-IA-no]

Outcome

Implements the pre-event Meta cutover against the deployed PMP Myth Bot contract while preserving the current registration and email-verification flow.

Closes #11
Closes #12
Closes #19
Coordinates with SairaAsua/proyecciones-mito#33.

Included

• preserves Nico Echaniz authorship for the useful commits from draft PRs feat: prepare registration-v4 legal contract #22 and feat: track canonical Meta CompleteRegistration #16 without modifying those branches;
• submits immutable registration-v4 while the backend accepts v3/v4 concurrently;
• emits CompleteRegistration only after canonical REGISTERED, including the email-code path, once per registration;
• requests authenticated commerce-status v2 only after the existing commerce claim;
• emits Purchase only from paid USD facts returned by the backend, with real value/currency and conversion_id as eventID;
• deduplicates refreshes, retries and state transitions;
• keeps undecided non-PII events for at most 24 hours; explicit decline clears them;
• moves the consent component into normal document flow before the footer and keeps registration/payment independent from consent;
• vendors byte-identical Meta commerce schemas, fixtures and manifest from the bot repository.

Verification

• npm test: 62 passed, 0 failed;
• npm run build: passed;
• node syntax checks: passed;
• contract SHA256SUMS: passed;
• byte comparison with PMP Myth Bot contracts: passed;
• git diff --check: passed.

Deliberately excluded

• no CAPI or Advanced Matching;
• no artificial purchase/refund;
• no evergreen agenda deployment before the August 8 event;
• [META-03][Nico+Julián] Verificar eventos y consentimiento en Meta Test Events #14 remains open until a legitimate consented purchase is observed in Meta Test Events.

No credentials, PII or Ticket Tailor provider identifiers are introduced.