Rackpad 1.9.0-beta.0

This beta follows the audit/notification fixes in
1.8.7-beta.1 with port filtering, inventory labels and Proxmox
host-import improvements. Rackpad V2 automation is outside this series.

• Cable creation has an initially off Hide Disabled Ports filter for both
  endpoints. Down and unknown ports remain available. Enabling the filter clears
  disabled selections. Editing an existing cable keeps disabled ports available.
• Labels lists inventory in the selected lab. Select devices or cables and
  explicitly generate immutable checked references. Repeating generation returns
  the same reference. Copy a reference, find it to navigate to its inventory, or
  print labels for selected records which already have references.
• Device references begin rpd1, cable references rpc1. Bech32m encodes 80 random
  bits with a checksum. Labels print the four-character prefix followed by groups
  of four and a final group of two, separated by ASCII hyphens. Lookup accepts
  this exact grouping or an ungrouped reference, in all lowercase or all uppercase.
  Mixed case, lookalikes, malformed groups and invalid checksums are rejected.
  The application never guesses a correction.
• References grant no access. Lookup and assignment require current lab read and
  write permissions respectively, including both labs for a cross-lab cable.
  No unauthenticated label endpoint is added. Existing IDs and links are retained.

New Proxmox API host imports now stage the management IPv4 address and actual
network interfaces. Missing hardware metadata stays unknown. Existing matched
hosts retain their manual fields, port IDs and cables; add missing fields in
inventory explicitly. The offline JSON collector remains available (#208).

Schema is 59 and adds nullable unique references to devices and cables with immutable
assignment triggers. Existing records receive no backfill. Logical and native
recovery preserve references and validate canonical values, type and uniqueness.
Assignment and deletion audit summaries retain the reference.

Rollback requires the previous binary/image paired with its pre-upgrade database,
configuration and encryption key. Do not run an older binary against schema 59.
Publication requires full technical gates and fresh-install, preceding-published-image
upgrade, persistence/restart and paired rollback on AMD64 and ARM64. Disposable
Docker acceptance does not establish real Proxmox guest installation, recovery or
hardware compatibility; those checks remain separate.