Rackpad 1.8.4-beta.7

This beta follows up on occupied rack placement and Diagram Visualizer text.
It carries the validated beta.6 candidate after renewal of the exact CodeQL
review pin for the unchanged SNMPv3 source. The beta.6 tag did not publish an
image or GitHub Release. Schema remains 52. There is no migration,
environment-variable, dependency, public API, or deployment change.

What to check

• #170: In Studio Beta, drag a device onto an occupied U or half-width slot,
  then try changing Start U to the same occupied position. The preview or error
  should name the conflicting device. Both devices should stay visible in their
  original positions after reload. Include a device with older rack-slot data
  if available; do not alter production inventory merely to create that case.
• #173: Check port lines in both Diagram Visualizer's Visible Links panel
  and Inspector → Direct connections. Each should have a space on both sides
  of “to”.
• #164: Retry appearance creation, reducing six bays to four, one-, three-,
  and sixteen-port NIC modules, portless fans, dragging module artwork, and
  save/reload/apply with a linked port. Report any remaining editor problem.

Smooth Managed front/rear routes through multiple guides, SVG/PNG exports, and
Orthogonal Managed right angles were verified on beta.5; #171 is closed.

Data and rollback

Existing overlapping records are preserved until explicitly moved. Rejected
placements do not move either device. Use a backup and the matching prior
application if a beta upgrade needs to be rolled back; this update does not
change the stored schema.

The beta branch and release-tag workflows must pass their required quality,
CodeQL, and security checks before this release is considered published.