feat: Story 022 — Device Provisioning

[iagocavalcante]

Summary

Implements Story 022: Device Provisioning — allows organizers to provision check-in devices for volunteers via short initialization tokens.

• Token generation — organizers generate 8-char codes (XXXX-XXXX) with 24h expiry, single use
• Device provisioning — volunteers enter token to provision their phone, receive long-lived API token
• Device management — admin LiveView listing all devices with status, last seen, and revoke action
• Revocation — organizer revokes access with confirmation, device can no longer authenticate
• Organization scoping — devices belong to one org, can only access that org's data
• Sidebar navigation — "Dispositivos" entry in org-level admin sidebar
• Provisioning API — POST /api/devices/provision (no auth, token IS the auth)

Files changed (9 files, ~450 lines)

Area	Files
Database	Migration: devices + device_init_tokens tables
Schemas	Device, DeviceInitToken
Context	Pretex.Devices — token gen, provisioning, auth, revocation
API	DeviceController — POST /api/devices/provision
LiveView	DeviceLive.Index — token display, device list, revoke
Navigation	Sidebar "Dispositivos" entry
Tests	13 tests covering all provisioning scenarios

Closes #22

Test plan

• All 1500 tests pass (0 failures)
• Compilation clean with --warnings-as-errors
• Manual: Navigate to org sidebar → Dispositivos link visible
• Manual: Generate token → 8-char code displayed
• Manual: curl -X POST /api/devices/provision -d '{"token":"XXXX-XXXX","device_name":"Test"}' → returns API token
• Manual: Device appears in list after provisioning
• Manual: Revoke device → status changes to "Revogado"
• Manual: Same token cannot be reused