Fix offline board flooding: fail-fast probe in hardware driver poll()

All three hardware drivers (Olimex, generic_esp32, generic_esp8266) now
probe with the first request and bail immediately on failure.

Before: offline board with 4 relays + 3 inputs = 7 requests × 3 s timeout
        = up to 21 s of blocking + 7 log lines per recheck cycle.
After:  exactly 1 request × 3 s timeout regardless of I/O count.

app/drivers/olimex_esp32_c6_evb/driver.py

@@ -83,26 +83,44 @@ class OlimexESP32C6EVBDriver(BoardDriver):
     # ── poll ──────────────────────────────────────────────────────────────────
 
     def poll(self, board: "Board") -> dict:
+        _offline = {"relay_states": {}, "input_states": {}, "is_online": False}
+
+        # ── Connectivity probe ─────────────────────────────────────────────
+        # Try the very first endpoint.  If the board doesn't reply we know
+        # it's offline and skip all remaining requests (saving N × 3 s worth
+        # of connect timeouts on every recheck cycle).
         relay_states: dict = {}
         input_states: dict = {}
-        online = False
 
-        for n in range(1, board.num_relays + 1):
+        if board.num_relays > 0:
+            probe = _get(f"{board.base_url}/relay/status?relay=1")
+            if probe is None:
+                return _offline
+            relay_states["relay_1"] = bool(probe.get("state", False))
+        elif board.num_inputs > 0:
+            probe = _get(f"{board.base_url}/input/status?input=1")
+            if probe is None:
+                return _offline
+            input_states["input_1"] = bool(probe.get("state", False))
+        else:
+            return _offline
+
+        # Board is reachable — collect remaining endpoints
+        for n in range(2, board.num_relays + 1):
             data = _get(f"{board.base_url}/relay/status?relay={n}")
             if data is not None:
                 relay_states[f"relay_{n}"] = bool(data.get("state", False))
-                online = True
 
-        for n in range(1, board.num_inputs + 1):
+        input_start = 2 if (board.num_relays == 0 and board.num_inputs > 0) else 1
+        for n in range(input_start, board.num_inputs + 1):
             data = _get(f"{board.base_url}/input/status?input={n}")
             if data is not None:
                 input_states[f"input_{n}"] = bool(data.get("state", True))
-                online = True
 
         return {
             "relay_states": relay_states,
             "input_states": input_states,
-            "is_online": online,
+            "is_online": True,
         }
 
     # ── webhook registration ──────────────────────────────────────────────────