feat(audit): comprehensive logging — auth events, severity, source, IP

Audit log was previously silent on authentication and on background
work. This wires:

- Login (success + failed) and logout via a wrapper around better-auth's
  [...all] handler. Failed logins are severity 'warning' and carry the
  attempted email so brute-force attempts surface in the inspector.
- New severity (info|warning|error|critical) and source (user|auth|
  system|webhook|cron|job) columns on audit_logs. permission_denied
  defaults to 'warning', hard_delete to 'critical'.
- Webhook delivery success/failure/DLQ/retry now write audit rows
  alongside the webhook_deliveries detail table.
- IP address is now visible as a column in the inspector (was already
  captured at the helper level).
- Audit UI: severity badges per row, severity + source dropdowns, IP
  column, expanded action filter covering hard-delete, webhook events,
  job/cron events.

Migration 0044 adds the two columns + their port-scoped indexes.
1175/1175 vitest passing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/db/schema/system.ts

@@ -41,6 +41,12 @@ export const auditLogs = pgTable(
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     revertOf: text('revert_of').references((): any => auditLogs.id),
     metadata: jsonb('metadata').default({}),
+    /** 'info' | 'warning' | 'error' | 'critical' — drives the row badge
+     *  in the inspector. Most user actions are 'info'. */
+    severity: text('severity').notNull().default('info'),
+    /** 'user' | 'system' | 'auth' | 'webhook' | 'cron' | 'job' — lets the
+     *  UI filter by event origin without grepping action names. */
+    source: text('source').notNull().default('user'),
     /** Full-text search column. Stored generated; updated by the migration's
      *  GENERATED ALWAYS expression covering action + entityType + entityId
      *  + actor email lookup. */
@@ -52,6 +58,8 @@ export const auditLogs = pgTable(
     index('idx_al_entity').on(table.entityType, table.entityId),
     index('idx_al_user').on(table.userId, table.createdAt),
     index('idx_al_created').on(table.createdAt),
+    index('idx_al_severity').on(table.portId, table.severity, table.createdAt),
+    index('idx_al_source').on(table.portId, table.source, table.createdAt),
   ],
 );