Add Grid Sensors device category to docs (and chase backend OEM additions: EdgeZero, Ting, Gridware)

Cyril asked in #website thread 1780486341.208049 (Victor cc'd) to add a grid sensors device category to https://docs.texturehq.com/integrations/manufacturers/devices-and-oems, with EdgeZero, Ting, and Gridware/Gridscope listed as Planned. Scope split: 1. apps/docs (mine): add 'grid_sensor' tab to DEVICE_TYPE_TABS in StaticManufacturersList.tsx. Tiny PR. Waiting on Victor's answer about whether to land it now (empty until backend) or wait for backend. 2. Backend manufacturers API (NOT mine): adding EdgeZero, Ting, Gridware as development-level manufacturers with grid_sensor device type to api.texturehq.com/v1/public/manufacturers. Need owner identified by Victor. Questions asked in-thread; idle until Victor or Cyril responds.