fix: use docker/telemetry/data/ for runtime data and add .gitignore

Move xrpld data paths from ./data/ to docker/telemetry/data/ so runtime
files stay within the docker telemetry directory. Add .gitignore to
exclude the data directory from version control.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker/telemetry/.gitignore

@@ -0,0 +1,2 @@
+# Runtime data generated by xrpld and telemetry stack
+data/

docker/telemetry/xrpld-telemetry.cfg

@@ -27,15 +27,15 @@ protocol = ws
 
 [node_db]
 type=NuDB
-path=./data/nudb
+path=docker/telemetry/data/nudb
 online_delete=256
 advisory_delete=0
 
 [database_path]
-./data
+docker/telemetry/data
 
 [debug_logfile]
-./data/debug.log
+docker/telemetry/data/debug.log
 
 [rpc_startup]
 { "command": "log_level", "severity": "debug" }