feat(interface_editor): add coerce_rnode_frequency_hz function for frequency conversion in Reticulum config

meshchatx/src/backend/interface_editor.py

@@ -1,7 +1,38 @@
 # SPDX-License-Identifier: 0BSD AND MIT
 
 
+def coerce_rnode_frequency_hz(value):
+    """Return RNode carrier frequency as integer Hz for Reticulum config.
+
+    Reticulum reads ``frequency`` with ``int()``; MHz-style decimals (868.825)
+    must not be stored verbatim or they truncate to invalid values. Accepts
+    Hz integers, bare MHz-style numbers below 1e6, and strings with optional
+    ghz/mhz/khz/hz suffix (ASCII, case-insensitive).
+    """
+    if value is None or value == "":
+        return value
+    raw = str(value).strip()
+    s = raw.lower().replace("_", "")
+    mult = 1.0
+    for suffix, m in (("ghz", 1e9), ("mhz", 1e6), ("khz", 1e3), ("hz", 1.0)):
+        if s.endswith(suffix):
+            s = s[: -len(suffix)].strip()
+            mult = m
+            break
+    f = float(s) * mult
+    if f <= 0:
+        return int(round(f))
+    if f >= 1_000_000:
+        return int(round(f))
+    is_integer = abs(f - round(f)) < 1e-9
+    if (not is_integer) or (is_integer and f < 10_000):
+        f *= 1_000_000.0
+    return int(round(f))
+
+
 class InterfaceEditor:
+    coerce_rnode_frequency_hz = staticmethod(coerce_rnode_frequency_hz)
+
     @staticmethod
     def update_value(interface_details: dict, data: dict, key: str):
         # update value if provided and not empty