Add: pair_devices.html template for device pairing interface

Fix:
- Polling intervals for SLMM.
-modem view now list
- device pairing much improved.
-various other tweaks through out UI.

backend/services/snapshot.py

@@ -108,6 +108,7 @@ def emit_status_snapshot():
                 "last_calibrated": r.last_calibrated.isoformat() if r.last_calibrated else None,
                 "next_calibration_due": r.next_calibration_due.isoformat() if r.next_calibration_due else None,
                 "deployed_with_modem_id": r.deployed_with_modem_id,
+                "deployed_with_unit_id": r.deployed_with_unit_id,
                 "ip_address": r.ip_address,
                 "phone_number": r.phone_number,
                     "hardware_model": r.hardware_model,
@@ -137,6 +138,7 @@ def emit_status_snapshot():
                     "last_calibrated": None,
                     "next_calibration_due": None,
                     "deployed_with_modem_id": None,
+                    "deployed_with_unit_id": None,
                     "ip_address": None,
                     "phone_number": None,
                     "hardware_model": None,