Filter browser-extension cookies from detection

Cookies set by browser extensions are not the website operator's
compliance responsibility. This adds stack-trace inspection to
filter out extension-originated document.cookie writes, and
annotates pre-existing cookies with a source field so operators
can triage them separately.

Introduces a CookieSource enum (SCRIPT / PRE_EXISTING) across
the full stack: PostgreSQL, coredata, service, HTTP handler, and
GraphQL schema. On conflict, source is upgraded from PRE_EXISTING
to SCRIPT when a page script is later observed setting the cookie.

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

pkg/coredata/migrations/20260429T064800Z.sql

@@ -0,0 +1,18 @@
+-- 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.
+
+CREATE TYPE cookie_source AS ENUM ('SCRIPT', 'PRE_EXISTING');
+
+ALTER TABLE cookies ADD COLUMN source cookie_source NOT NULL DEFAULT 'PRE_EXISTING';
+ALTER TABLE cookies ALTER COLUMN source DROP DEFAULT;