Fix ticket_watchers.ticket_id type mismatch and missing FK (#32)

ticket_watchers.ticket_id was int(11) while every other satellite
table (ticket_comments, ticket_attachments, ticket_dependencies,
custom_field_values) uses varchar(9)/varchar(10) matching
tickets.ticket_id, and it had no FK constraint at all — unlike every
other satellite table — so orphaned watcher rows could never be
caught by referential integrity.

Changed the column to varchar(9) with an ON DELETE CASCADE FK to
tickets, in both 000_baseline.sql and a new idempotent
004_fix_ticket_watchers_type.sql (which also deletes any pre-existing
orphaned watcher rows before adding the constraint, since orphans
would otherwise make the ADD CONSTRAINT fail). Updated
watch_ticket.php, NotificationHelper::notifyWatchers(), and
notifications.php's audit-log JOIN to bind/compare ticket_id as a
string instead of casting to int, including replacing a fragile
CAST(entity_id AS UNSIGNED) with a direct string comparison.

Verified against real MariaDB: applied 004 against a simulated
pre-fix deployment with one valid and one orphaned watcher row —
the orphan is removed, the column converts losslessly, the FK is
added, and the migration is idempotent on re-run. Confirmed
ON DELETE CASCADE actually removes watchers when their ticket is
deleted, that inserting a watcher for a nonexistent ticket now fails
with a real FK violation, and exercised the updated watch/unwatch and
status-change-notification query paths end-to-end against the fixed
schema.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015nCxwFFsy8ouMWzn56rPVP

migrations/000_baseline.sql

@@ -243,11 +243,12 @@ CREATE TABLE IF NOT EXISTS `ticket_templates` (
 
 -- ============ ticket_watchers ============
 CREATE TABLE IF NOT EXISTS `ticket_watchers` (
-  `ticket_id` int(11) NOT NULL,
+  `ticket_id` varchar(9) NOT NULL,
   `user_id` int(11) NOT NULL,
   `created_at` timestamp NOT NULL DEFAULT current_timestamp(),
   PRIMARY KEY (`ticket_id`,`user_id`),
-  KEY `idx_watcher_user` (`user_id`)
+  KEY `idx_watcher_user` (`user_id`),
+  CONSTRAINT `fk_watchers_ticket_id` FOREIGN KEY (`ticket_id`) REFERENCES `tickets` (`ticket_id`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
 
 -- ============ tickets ============

migrations/004_fix_ticket_watchers_type.sql

@@ -0,0 +1,28 @@
+-- Fix ticket_watchers.ticket_id type mismatch and missing FK to tickets
+--
+-- ticket_watchers.ticket_id was int(11), while every other satellite table
+-- (ticket_comments, ticket_attachments, ticket_dependencies,
+-- custom_field_values) stores it as varchar(9)/varchar(10) matching
+-- tickets.ticket_id. There was also no FK constraint at all, unlike every
+-- other satellite table, so orphaned watcher rows could never be caught by
+-- referential integrity. Ticket IDs are always 9-digit numeric strings
+-- (see TicketModel::create's sprintf('%09d', ...)), so the int -> varchar(9)
+-- conversion below is lossless for real data.
+--
+-- Safe to re-run.
+
+-- Remove any watcher rows that no longer point at a real ticket (possible
+-- today precisely because there was no FK to prevent it) before adding the
+-- constraint, since orphans would make the ADD CONSTRAINT below fail.
+DELETE tw FROM `ticket_watchers` tw
+    LEFT JOIN `tickets` t ON tw.`ticket_id` = t.`ticket_id`
+    WHERE t.`ticket_id` IS NULL;
+
+ALTER TABLE `ticket_watchers`
+    MODIFY COLUMN `ticket_id` varchar(9) NOT NULL;
+
+ALTER TABLE `ticket_watchers`
+    DROP FOREIGN KEY IF EXISTS `fk_watchers_ticket_id`;
+
+ALTER TABLE `ticket_watchers`
+    ADD CONSTRAINT `fk_watchers_ticket_id` FOREIGN KEY (`ticket_id`) REFERENCES `tickets` (`ticket_id`) ON DELETE CASCADE;