Give the Influx and MQTT nodes their two missing knobs

The Influx client was built with no timeout, so every query and write fell
through to influxdb-client's own 10 s default — invisible to a flow and
unchangeable. The param is in seconds like its peers; the client counts in
milliseconds, so the call sites convert.

The publisher backlog was a module constant, read once at import. It is the
depth at which the oldest payload is dropped and the node goes degraded, and
a node that bursts wants more than one that trickles, so it moves to Params
and is read where the queue is built.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K1moruzue2kTJd3uVisgNk

backend/fluksio/flow/nodes/influx.py

@@ -58,6 +58,7 @@ class InfluxDbNode(Node):
         - ``bucket`` (str): Bucket name (required)
         - ``write_precision`` (str): Write precision ("ns", "us", "ms", "s"), default "ms"
         - ``query_range`` (str): Default time range for queries, e.g., "-1h", "-24h"
+        - ``timeout`` (float): Deadline for a request in seconds (default: 10.0)
         - ``writes`` (dict): Write configurations keyed by message name, each with:
             - ``measurement`` (str): Measurement name to write to
             - ``field`` (str): Field name to write (default: "value")
@@ -154,6 +155,7 @@ class InfluxDbNode(Node):
         "bucket",
         "write_precision",
         "query_range",
+        "timeout",
         "writes",
         "queries",
         "_write_client",
@@ -169,6 +171,14 @@ class InfluxDbNode(Node):
         bucket: str
         write_precision: str = "ms"
         query_range: str = "-1h"
+        # Bounds every request to the server. Without one the client falls
+        # back to its own default, which no flow can see or change. Held in
+        # seconds like every other node; the client counts in milliseconds.
+        timeout: float = Field(
+            default=10.0,
+            gt=0,
+            description="Give up on a query or write after this many seconds.",
+        )
         # Per-port write and query configuration.
         writes: dict[str, dict[str, Any]] = {}
         queries: dict[str, dict[str, Any]] = {}
@@ -201,6 +211,7 @@ class InfluxDbNode(Node):
         self.bucket = cfg.bucket
         self.write_precision = cfg.write_precision
         self.query_range = cfg.query_range
+        self.timeout = cfg.timeout
         self.writes = cfg.writes
         self.queries = cfg.queries
 
@@ -285,7 +296,12 @@ class InfluxDbNode(Node):
         echo = {key: value for key, value in request.items() if key != "flux"}
 
         logger.info("Running Flux for node '%s': %s", self.name, flux)
-        with InfluxDBClient(url=self.url, token=self.token, org=self.org) as client:
+        with InfluxDBClient(
+            url=self.url,
+            token=self.token,
+            org=self.org,
+            timeout=int(self.timeout * 1000),
+        ) as client:
             tables = client.query_api().query(flux, org=self.org)
 
         rows = [
@@ -326,7 +342,12 @@ class InfluxDbNode(Node):
         from influxdb_client.client.write_api import SYNCHRONOUS
 
         try:
-            with InfluxDBClient(url=self.url, token=self.token, org=self.org) as client:
+            with InfluxDBClient(
+                url=self.url,
+                token=self.token,
+                org=self.org,
+                timeout=int(self.timeout * 1000),
+            ) as client:
                 write_api = client.write_api(write_options=SYNCHRONOUS)
 
                 precision_map = {
@@ -422,7 +443,12 @@ class InfluxDbNode(Node):
         results = {}
 
         try:
-            with InfluxDBClient(url=self.url, token=self.token, org=self.org) as client:
+            with InfluxDBClient(
+                url=self.url,
+                token=self.token,
+                org=self.org,
+                timeout=int(self.timeout * 1000),
+            ) as client:
                 query_api = client.query_api()
 
                 for spec in self.output_ports: