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.

tests/test_dnsmasq.py

@@ -1,25 +1,28 @@
-import sys
 from unittest.mock import patch
 
 import pytest
 
-sys.path.insert(0, "/home/wall/vacuum-wall")
-
 from lib import dnsmasq
 
 
 @pytest.fixture
 def temp_data_dir(tmp_path):
+    original_config_dir = dnsmasq.CONFIG_DIR
     original = dnsmasq.DATA_DIR
     original_config = dnsmasq.CONFIG_PATH
+    original_fragments = dnsmasq.FRAGMENTS_DIR
+    dnsmasq.CONFIG_DIR = tmp_path / "dnsmasq"
     dnsmasq.DATA_DIR = tmp_path / "dnsmasq"
-    dnsmasq.CONFIG_PATH = dnsmasq.DATA_DIR / "config.json"
+    dnsmasq.CONFIG_PATH = dnsmasq.CONFIG_DIR / "config.json"
     dnsmasq.FRAGMENTS_DIR = dnsmasq.DATA_DIR / "fragments"
+    dnsmasq.CONFIG_DIR.mkdir(parents=True, exist_ok=True)
     dnsmasq.DATA_DIR.mkdir(parents=True, exist_ok=True)
     dnsmasq.FRAGMENTS_DIR.mkdir(parents=True, exist_ok=True)
     yield tmp_path
+    dnsmasq.CONFIG_DIR = original_config_dir
     dnsmasq.DATA_DIR = original
     dnsmasq.CONFIG_PATH = original_config
+    dnsmasq.FRAGMENTS_DIR = original_fragments
 
 
 class TestDeepMerge: