feat: router simulator

[NickGhignatti]

This pull request implements building-scoped device keys for telemetry collectors, extends the telemetry API with new endpoints, and refines how routers and connected devices are handled. It introduces a device key epoch for secure key rotation, adds support for router simulation, and ensures that both /telemetry/ingest and /telemetry/collector are ungated at the edge but HMAC-verified in-service. The changes also update documentation and acceptance tests to reflect these new behaviors.

API and Security Enhancements:

• Added /collector endpoint to the telemetry API, allowing on-site collectors to fetch router lists, authenticated using a building-scoped device key derived from a master key and a per-building epoch. The endpoint is ungated at the edge and requires a signed timestamp for authentication. [1] [2] [3] [4]
• Introduced /device-keys/buildings/{buildingId} endpoint to rotate and issue new device keys per building, with device keys derived (not stored) using TELEMETRY_DEVICE_MASTER_KEY and a per-building epoch. [1] [2] [3] [4] [5] [6] [7]

Router and Device Management:

• Added /connected-devices/buildings/{buildingId} endpoint to return the total number of devices connected in a building, summing the latest reports from each room without double-counting. [1] [2] [3]
• Extended the simulator configuration to support router simulation by adding ap-simulator for the router kind and clarified that only claimed kinds are sent for simulation. [1] [2] [3]

Database and Storage Changes:

• Added device_key_epoch column to the buildings table to track device key rotations, with migrations to add and remove the column. [1] [2]
• Implemented DeviceKeyStore for Postgres, supporting retrieval and rotation of the device key epoch. [1] [2]

Testing and Documentation:

• Updated acceptance tests to verify that /telemetry/collector is ungated at the edge and HMAC-verified in-service, and added helper methods for collector authentication. [1] [2]
• Improved documentation and comments throughout to clarify the handling of device keys, router simulation, and authenticated endpoints. [1] [2] [3]

Other Notable Changes:

• Added a new method to fetch all sensors of a particular type from the database, supporting router enumeration for collectors.

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References:
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]

Closes #433