M1 Beta: Implement local ESP web management concept

[mastertape]

Roadmap reference: docs/roadmap/m1-dhl-retrofit-beta.md

Define and later implement the local ESP web interface for beta configuration without cloud.

Acceptance criteria:

• Web UI can manage 4 households.
• Each household can contain up to 2 people.
• PINs can be created, edited and disabled.
• NFC tokens can be enrolled, assigned and disabled.
• Fingerprint identities are represented as prepared/optional.
• Up to 6 carrier PINs can be configured.
• Identity-to-household assignment is visible.
• No cloud, bridge or Home Assistant is required for configuration.
• Security notes for local admin access are documented.

[mastertape]

Progress update:

• The standalone management requirement has now been captured in the OpenParcelLock repository:
  OpenParcelBox/openparcellock/docs/standalone-management.md
• The requirement is now explicit: a standalone OpenParcelBox controller should provide AP-mode setup and embedded local web management without requiring cloud, bridge, Home Assistant, MQTT or a vendor app.

This issue should stay open because the actual M1 web management concept is not designed or implemented yet.

Remaining work includes:

• define the ESP-side web UI scope
• define local admin/recovery handling
• define household/person/PIN/NFC management screens and API
• document security notes for local admin access
• later implement and test the web management path