Add PostHog consent integration and extract integration plugin system

Add PostHog opt-in/opt-out consent support mirroring the existing Google
Consent Mode integration: database column, GraphQL field, console UI
toggle, and client-side posthog-js calls.

Extract both GCM and PostHog logic from CookieBannerClient into a
ConsentIntegration plugin interface so future integrations can be added
without modifying the client core.

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/coredata/cookie_banner_version.go

@@ -55,6 +55,7 @@ type (
 		Kind            CookieCategoryKind `json:"kind"`
 		Cookies         CookieItems        `json:"cookies"`
 		GCMConsentTypes []string           `json:"gcm_consent_types"`
+		PostHogConsent  bool               `json:"posthog_consent"`
 	}
 
 	CookieBannerVersion struct {

pkg/coredata/cookie_category.go

@@ -48,6 +48,7 @@ type (
 		Kind            CookieCategoryKind `db:"kind"`
 		Rank            int                `db:"rank"`
 		GCMConsentTypes []string           `db:"gcm_consent_types"`
+		PostHogConsent  bool               `db:"posthog_consent"`
 		CreatedAt       time.Time          `db:"created_at"`
 		UpdatedAt       time.Time          `db:"updated_at"`
 	}
@@ -111,6 +112,7 @@ SELECT
 	kind,
 	rank,
 	gcm_consent_types,
+	posthog_consent,
 	created_at,
 	updated_at
 FROM
@@ -162,6 +164,7 @@ SELECT
 	kind,
 	rank,
 	gcm_consent_types,
+	posthog_consent,
 	created_at,
 	updated_at
 FROM
@@ -241,6 +244,7 @@ SELECT
 	kind,
 	rank,
 	gcm_consent_types,
+	posthog_consent,
 	created_at,
 	updated_at
 FROM
@@ -289,6 +293,7 @@ INSERT INTO cookie_categories (
 	kind,
 	rank,
 	gcm_consent_types,
+	posthog_consent,
 	created_at,
 	updated_at
 ) VALUES (
@@ -302,6 +307,7 @@ INSERT INTO cookie_categories (
 	@kind,
 	@rank,
 	@gcm_consent_types,
+	@posthog_consent,
 	@created_at,
 	@updated_at
 )
@@ -318,6 +324,7 @@ INSERT INTO cookie_categories (
 		"kind":              c.Kind,
 		"rank":              c.Rank,
 		"gcm_consent_types": c.GCMConsentTypes,
+		"posthog_consent":   c.PostHogConsent,
 		"created_at":        c.CreatedAt,
 		"updated_at":        c.UpdatedAt,
 	}
@@ -347,6 +354,7 @@ SET
 	slug = @slug,
 	description = @description,
 	gcm_consent_types = @gcm_consent_types,
+	posthog_consent = @posthog_consent,
 	updated_at = @updated_at
 WHERE
 	%s
@@ -361,6 +369,7 @@ WHERE
 		"slug":              c.Slug,
 		"description":       c.Description,
 		"gcm_consent_types": c.GCMConsentTypes,
+		"posthog_consent":   c.PostHogConsent,
 		"updated_at":        c.UpdatedAt,
 	}
 	maps.Copy(args, scope.SQLArguments())
@@ -477,6 +486,7 @@ SELECT
 	kind,
 	rank,
 	gcm_consent_types,
+	posthog_consent,
 	created_at,
 	updated_at
 FROM

pkg/coredata/migrations/20260424T112802Z.sql

@@ -0,0 +1,16 @@
+-- Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+-- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+-- AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+-- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+-- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+-- OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+-- PERFORMANCE OF THIS SOFTWARE.
+
+ALTER TABLE cookie_categories ADD COLUMN posthog_consent BOOLEAN NOT NULL DEFAULT false;
+ALTER TABLE cookie_categories ALTER COLUMN posthog_consent DROP DEFAULT;