feat: watcher/CC system, SLA engine, and rich text comments

- Watcher system: ticket_watchers table, watch/unwatch endpoints,
  notifications to watchers on comments and updates, watcher/cc
  recipient sources in SendEmail scrip action, watch toggle and
  watcher avatars in ticket detail UI
- SLA engine: sla_policies table, SLA deadline columns on tickets,
  CRUD routes, OnSlaBreach scrip condition, scheduler SLA calculation,
  deadlines set on create/reply, cleared on resolve, SLA indicators
  on ticket list and detail, SLA Policies tab in admin
- Rich text: marked-based markdown rendering with XSS safety,
  Write/Preview toggle in comment composer, styled prose output

drizzle/migrations/0019_watcher_tables.sql

@@ -0,0 +1,9 @@
+CREATE TABLE ticket_watchers (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  ticket_id INTEGER NOT NULL REFERENCES tickets(id) ON DELETE CASCADE,
+  user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  UNIQUE(ticket_id, user_id)
+);
+CREATE INDEX ticket_watchers_ticket_id_idx ON ticket_watchers(ticket_id);
+CREATE INDEX ticket_watchers_user_id_idx ON ticket_watchers(user_id);

drizzle/migrations/0020_sla_tables.sql

@@ -0,0 +1,15 @@
+CREATE TABLE sla_policies (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  queue_id UUID REFERENCES queues(id) ON DELETE SET NULL,
+  name TEXT NOT NULL,
+  description TEXT,
+  response_time_minutes INTEGER,
+  resolution_time_minutes INTEGER,
+  disabled BOOLEAN NOT NULL DEFAULT false,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX sla_policies_queue_id_idx ON sla_policies(queue_id);
+
+ALTER TABLE tickets ADD COLUMN sla_response_deadline TIMESTAMPTZ;
+ALTER TABLE tickets ADD COLUMN sla_resolution_deadline TIMESTAMPTZ;
+ALTER TABLE tickets ADD COLUMN sla_breached TEXT;

drizzle/migrations/meta/_journal.json

@@ -134,6 +134,20 @@
       "when": 1781551130161,
       "tag": "0018_dapper_jack_power",
       "breakpoints": true
+    },
+    {
+      "idx": 19,
+      "version": "7",
+      "when": 1781552000000,
+      "tag": "0019_watcher_tables",
+      "breakpoints": true
+    },
+    {
+      "idx": 20,
+      "version": "7",
+      "when": 1781552001000,
+      "tag": "0020_sla_tables",
+      "breakpoints": true
     }
   ]
 }