chore: rename remaining subfeed references to siftlode

Replace the leftover 'subfeed' name across logger names + log_config,
frontend localStorage keys, Postgres user/db/volume defaults in the
compose files, .env.example, config.py, backup/restore scripts and the
README. Pure rename; no behavioural change. localStorage keys move from
subfeed.* to siftlode.* (one-time UI-state reset is acceptable).

backend/app/main.py

@@ -5,20 +5,20 @@ from pathlib import Path
 
 from fastapi import FastAPI, HTTPException
 
-# When started via uvicorn --log-config the "subfeed" logger is already configured
+# When started via uvicorn --log-config the "siftlode" logger is already configured
 # (see log_config.json). This block is a timestamped fallback for other entrypoints
 # (tests, scripts) so our logs are never silently dropped.
-_subfeed_logger = logging.getLogger("subfeed")
-if not _subfeed_logger.handlers:
+_siftlode_logger = logging.getLogger("siftlode")
+if not _siftlode_logger.handlers:
     _handler = logging.StreamHandler(sys.stdout)
     _handler.setFormatter(
         logging.Formatter("%(asctime)s %(levelname)-5s [%(name)s] %(message)s")
     )
-    _subfeed_logger.addHandler(_handler)
-    _subfeed_logger.setLevel(logging.INFO)
-    _subfeed_logger.propagate = False
+    _siftlode_logger.addHandler(_handler)
+    _siftlode_logger.setLevel(logging.INFO)
+    _siftlode_logger.propagate = False
 
-log = logging.getLogger("subfeed.app")
+log = logging.getLogger("siftlode.app")
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import FileResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles