fix(privacy): separate analytics consent from email consent (#56)

The previous commit widened the marketing consent sentence to cover the Brevo tracker, so one checkbox carried both purposes. That is the specific pattern GDPR rejects: consent has to be granular, and current EDPB guidance treats bundling tracking consent with subscription consent as invalid because the customer cannot accept one purpose and refuse the other. Quebec's Law 25 s.8.1 is stricter again — profiling technology has to be off until the person switches it on, with no pre-ticked box and no consent inherited from agreeing to something else. Building to both standards was the decision, since the storefront is publicly reachable and anyone can register.

So the marketing sentence is restored to exactly what it was, which leaves every existing email consent valid and untouched, and analytics gets its own column, its own sentence, its own checkbox at registration, its own toggle in the account page and its own endpoint. A customer can now hold either, both, or neither, and withdrawing one does not disturb the other.

The migration defaults analytics_consent to false, which is both the honest answer — none of the existing customers was ever asked — and what Law 25 requires. Nothing about this change opts anybody in.

Two details that are compliance requirements rather than wording preferences. The sentence names Brevo instead of saying "our email provider", because informed consent means the customer can tell who receives their data and a description they cannot act on is not disclosure. And the account toggle is as prominent and as easy to switch off as it is to switch on, because withdrawal has to be as easy as consenting.

The analytics endpoint is separate from the marketing one rather than a second field on it, so that a single call cannot change an answer the customer did not touch — the bundling problem moved from the form into the API. The unit tests now assert the two consents stay apart in both directions, including that the marketing sentence still says nothing about tracking, because re-bundling them would otherwise pass silently and is the mistake this project already made once.

Verified: backend tsc clean, both lint suites 0 errors with no new warnings, 478 unit tests passing across 33 suites, frontend production build green. Not verified: the migration has not been run against a database, and integration and e2e need a Node this machine does not have active. None of this is legal advice and the wording is worth a lawyer's eye before it ships.

Refs #56

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/src/utils.ts

@@ -72,22 +72,37 @@ export function tagColorFor(name: string): string {
 }
 
 /**
- * Widened for #56 to cover analytics as well as email.
+ * Email marketing only. Deliberately says nothing about tracking.
  *
- * The previous wording named only emails. Gating the Brevo tracker on
- * `marketing_consent` while that sentence was the thing customers agreed to
- * would have treated "email me about new items" as authorisation to send their
- * browsing to a third party, which it plainly did not say.
+ * This was briefly widened during #56 to cover analytics as well, and that was
+ * wrong: GDPR requires consent to be granular, and current EDPB guidance treats
+ * bundling tracking consent with subscription consent as invalid because the
+ * customer cannot accept one purpose and refuse the other. Quebec's Law 25 is
+ * stricter still. Analytics has its own sentence and its own column below.
  *
- * Changing the sentence does not retroactively widen anyone's consent, because
- * `marketing_consent_text` records what each customer was actually shown.
- * Everyone who agreed to the old wording keeps their email consent and is not
- * tracked; see `analyticsConsent` in routes/customers.ts, which is what the
- * tracker is gated on. That is the whole reason this string is stored per
- * customer rather than assumed.
+ * Left exactly as it was so that every existing consent record stays valid and
+ * untouched — nobody has to be re-asked for something they already agreed to.
  */
 export const MARKETING_CONSENT_TEXT =
-  'I want to receive occasional emails about new one-of-a-kind items from Redefined Designs, and I agree that what I browse and buy here may be shared with our email provider to help choose what they contain. I can unsubscribe at any time.';
+  'I want to receive occasional emails about new one-of-a-kind items from Redefined Designs. I can unsubscribe at any time.';
+
+/**
+ * Consent to the Brevo tracker (#56). Separate from marketing consent, and
+ * separately refusable, because they are two purposes with two recipients.
+ *
+ * Names Brevo rather than saying "our email provider": informed consent means
+ * the customer can tell who receives their data, and a description they cannot
+ * act on is not disclosure. Says what is shared and why, states that it is
+ * optional and independent of the emails, and states that it can be turned off
+ * — withdrawal has to be as easy as giving it.
+ *
+ * Stored verbatim in `analytics_consent_text` for the same reason the marketing
+ * sentence is: a record of consent that does not say what was consented to
+ * cannot be audited, and re-wording this later must not silently broaden
+ * anybody's agreement.
+ */
+export const ANALYTICS_CONSENT_TEXT =
+  'I agree that what I browse and buy on this site may be shared with Brevo, the service that sends our emails, so that what they contain is relevant to me. This is optional, separate from receiving the emails themselves, and I can turn it off at any time.';
 
 /**
  * Strips trailing slashes so a base URL can be joined with a stored path.