feat: report facts, not warnings (0.2.0)

Drop get_device_warnings. The DSL noise margin and the firmware on offer
are already facts in get_system_config (dsl_downstream_noise_margin,
firmware_update_available, firmware_version); netOrk derives
dsl_snr_low and firmware_update_available from them (netOrk #1111).

napalm_fritzbox/fritzbox.py

@@ -395,39 +395,6 @@ class FritzBoxDriver(ResidentialGatewayDriver):
 
         return result
 
-    def get_device_warnings(self) -> list[dict[str, Any]]:
-        """Return device warnings derived from DSL line quality and firmware state.
-
-        Called during the poll cycle via ``_collect_system_snapshots``.
-        Reads ``UserInterface1`` for firmware updates and
-        ``WANDSLInterfaceConfig1`` for line quality.
-        """
-        warnings: list[dict[str, Any]] = []
-        available = self.fc.services if self.fc else {}
-
-        if "UserInterface1" in available:
-            try:
-                ui_info = self._call("UserInterface1", "X_AVM-DE_GetInfo")
-                if ui_info.get("NewX_AVM-DE_UpdateState", "") == "Available":
-                    warnings.append({
-                        "code": "firmware_update_available",
-                        "meta": {"latest_version": ui_info.get("NewX_AVM-DE_Version", "")},
-                    })
-            except _OPTIONAL_SERVICE_ERRORS:
-                pass
-
-        if "WANDSLInterfaceConfig1" in available:
-            try:
-                info = self._call("WANDSLInterfaceConfig1", "GetInfo")
-                # SNR margin is in dB×10; < 60 means < 6 dB — borderline line quality
-                snr_down = int(_to_float(info.get("NewDownstreamNoiseMargin")))
-                if 0 < snr_down < 60:
-                    warnings.append({"code": "dsl_snr_low", "meta": {"snr_db_x10": snr_down}})
-            except _OPTIONAL_SERVICE_ERRORS:
-                pass
-
-        return warnings
-
     def get_arp_table(self, vrf: str = "") -> list[dict[str, Any]]:
         """Return the ARP table, derived from :meth:`get_hosts`.