Restrict API keys to public-visibility tickets by default (#70)

api/tickets_api.php (both the single-ticket read and the list/triage
path) bypassed ticket visibility entirely for any 'read'-scope key,
regardless of who it was issued to or what it was for — any key got
blanket read access to Confidential and Internal ticket titles,
descriptions, and comments, with no way to scope a key more narrowly.

Added see_all_visibility to api_keys (migration 006), defaulting to
false for both new and existing keys — the prior blanket-access
behavior is what's being restricted here, so unlike scope's own
un-migrated-database fallback (which defaults toward preserving old
behavior), a missing/null value here defaults to the new, restrictive
one. An admin can opt a specific key in via a new checkbox in the API
Key Management UI when it genuinely needs the full queue.

tickets_api.php now builds a synthetic "no special access" user and
runs it through TicketModel's existing per-user visibility plumbing
(getVisibilityFilter/canUserAccessTicket) instead of a separate SQL
path, so this stays in lockstep with however visibility rules evolve
for real users. That synthetic user_id is -1, not 0: testing surfaced
that canUserAccessTicket()'s confidential-ticket check does a PHP-level
(int) cast, and (int)null === 0, so an unassigned confidential ticket's
NULL assigned_to would otherwise false-positive-match a user_id of 0.

Verified against real MariaDB with public/confidential/internal test
tickets: a public-only-scoped key's list only returns the public
ticket, and canUserAccessTicket() correctly returns false for both the
confidential ticket (unassigned, then reassigned to a real user — both
cases) and the internal one; a see_all_visibility key sees all three,
unchanged from the prior behavior. Also verified createKey()/
validateKey()'s default-false and explicit-true paths round-trip
correctly through the real DB.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0117oBw2jN4kALYeS8HPq4zV

middleware/ApiKeyAuth.php

@@ -37,6 +37,7 @@ class ApiKeyAuth
     {
         $this->keyContext = [
             'scope' => $keyData['scope'] ?? 'read_write',
+            'see_all_visibility' => !empty($keyData['see_all_visibility']),
             'key_name' => $keyData['key_name'] ?? null,
             'created_by' => $keyData['created_by'] ?? null,
             'api_key_id' => $keyData['api_key_id'] ?? null,
@@ -46,7 +47,7 @@ class ApiKeyAuth
     /**
      * Get the context of the authenticated API key.
      *
-     * @return array|null ['scope', 'key_name', 'created_by', 'api_key_id'] or null
+     * @return array|null ['scope', 'see_all_visibility', 'key_name', 'created_by', 'api_key_id'] or null
      */
     public function getKeyContext(): ?array
     {