MCP: ticket links and similar-ticket search (#113)

- get_ticket now returns `links` (blocks / blocked_by / relates_to /
  duplicates / duplicated_by, phrased from this ticket's side, limited to
  linked tickets the user can see) and `blocked` (any open blocked_by).
- find_similar_tickets (tickets:read): the possible-duplicates finder, by
  title or by an existing ticket (which is excluded from the results).
- link_tickets / unlink_tickets (tickets:write). Marking a duplicate only
  records the link. unlink also finds a link stored from the other side
  ("B blocked_by A" for "A blocks B").

api/ticket_dependencies.php's list/add/remove logic moves to
services/DependencyService.php, used by both (same checks and messages).
DependencyModel's remove methods now return rows removed, so removing a
link that is already gone no longer writes a "deleted" audit row.

Also includes the port in ToolScopeMiddleware's resource_metadata URL
(matches the 401's; no effect on prod, which has no port).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MGDKHiU5RJdo3dqQUDow3X

models/DependencyModel.php

@@ -219,14 +219,14 @@ class DependencyModel
      * Remove a dependency
      *
      * @param int $dependencyId Dependency ID
-     * @return bool Success status
+     * @return int|false Rows removed (0 if it no longer existed), or false on failure
      */
     public function removeDependency($dependencyId)
     {
         $sql = "DELETE FROM ticket_dependencies WHERE dependency_id = ?";
         $stmt = $this->conn->prepare($sql);
         $stmt->bind_param("i", $dependencyId);
-        $result = $stmt->execute();
+        $result = $stmt->execute() ? $stmt->affected_rows : false;
         $stmt->close();
         return $result;
     }
@@ -237,7 +237,7 @@ class DependencyModel
      * @param string $ticketId Source ticket ID
      * @param string $dependsOnId Target ticket ID
      * @param string $type Dependency type
-     * @return bool Success status
+     * @return int|false Rows removed (0 if no such link), or false on failure
      */
     public function removeDependencyByTickets($ticketId, $dependsOnId, $type)
     {
@@ -245,7 +245,7 @@ class DependencyModel
                 WHERE ticket_id = ? AND depends_on_id = ? AND dependency_type = ?";
         $stmt = $this->conn->prepare($sql);
         $stmt->bind_param("sss", $ticketId, $dependsOnId, $type);
-        $result = $stmt->execute();
+        $result = $stmt->execute() ? $stmt->affected_rows : false;
         $stmt->close();
         return $result;
     }