Migrate declarative configs to config/ dir and remove hardcoded paths

Replace all hardcoded /home/wall/vacuum-wall paths in lib/ with Path(__file__).resolve()
auto-discovery. Move config files from data/ to config/<subsystem>/config.json.
ACME now uses ACME_HOME env var and data/acme/ for cert storage. Systemd units
and sudoers use {{ USER_NAME }}, {{ PROJECT_DIR }}, {{ ACME_HOME }} Jinja2
template variables for install-time substitution. Remove sys.path.insert boot
strap from test files.

lib/dnsmasq.py

@@ -15,9 +15,10 @@ from typing import Any
 
 from jinja2 import Environment, FileSystemLoader
 
-PROJECT_DIR = Path("/home/wall/vacuum-wall")
+PROJECT_DIR = Path(__file__).resolve().parent.parent
+CONFIG_DIR = PROJECT_DIR / "config" / "dnsmasq"
 DATA_DIR = PROJECT_DIR / "data" / "dnsmasq"
-CONFIG_PATH = DATA_DIR / "config.json"
+CONFIG_PATH = CONFIG_DIR / "config.json"
 FRAGMENTS_DIR = DATA_DIR / "fragments"
 DNSMASQ_CONF = "/etc/dnsmasq.d/vacuum-wall.conf"
 LEASE_FILE = "/var/lib/dnsmasq/dnsmasq.leases"
@@ -46,6 +47,7 @@ DEFAULT_CFG: dict[str, Any] = {
 
 
 def _ensure_dirs() -> None:
+    CONFIG_DIR.mkdir(parents=True, exist_ok=True)
     DATA_DIR.mkdir(parents=True, exist_ok=True)
     FRAGMENTS_DIR.mkdir(parents=True, exist_ok=True)