refactor: replace array-based expressions with typed class hierarchy

Replace the old Lisp-like array expression representation
(["AND", ["PARAM", ...], ...]) with a class hierarchy rooted in
an abstract Expression class (Literal, Parameter, Binary, Unary,
FunctionCall, Conditional). This gives compile-time type safety
to expression construction, evaluation, and pattern matching.

Key changes:
- New lib/common/expression.ts defines the class hierarchy with
  map/evaluate/toString methods
- Rewrite parser as hand-rolled recursive descent, removing the
  parsimmon dependency
- Extend Path with a colon separator to unify parameter identity
  and attributes into a single address space (e.g.
  "Device.WiFi.SSID.1.Name:writable"). The colon field tracks
  how many trailing segments are attribute qualifiers. PathSet
  rewritten with separate param/attr segment indexes
- Flatten device attribute representation in the UI to
  colon-delimited keys mirroring the new path syntax

ui/overview-page.ts

@@ -1,31 +1,29 @@
-import { ClosureComponent, Component } from "mithril";
+import { ClosureComponent } from "mithril";
 import { m } from "./components.ts";
-import config from "./config.ts";
+import { overview } from "./config.ts";
 import * as store from "./store.ts";
 import pieChartComponent from "./pie-chart-component.ts";
 
-const GROUPS = config.ui.overview.groups || {};
-const CHARTS = {};
-for (const group of Object.values(GROUPS)) {
-  for (const chartName of Object.values(group["charts"]) as string[])
-    CHARTS[chartName] = config.ui.overview.charts[chartName];
+const GROUPS = overview.groups;
+const CHARTS: typeof overview.charts = {};
+for (const group of GROUPS) {
+  for (const chartName of group.charts)
+    CHARTS[chartName] = overview.charts[chartName];
 }
 
-function queryCharts(charts: Record<string, unknown>): Record<string, unknown> {
+function queryCharts(charts: typeof overview.charts): typeof charts {
   charts = Object.assign({}, charts);
   for (let [chartName, chart] of Object.entries(charts)) {
-    charts[chartName] = chart = Object.assign({}, chart);
-    chart["slices"] = Object.assign({}, chart["slices"]);
-    for (let [sliceName, slice] of Object.entries(chart["slices"])) {
-      const filter = slice["filter"];
-      chart["slices"][sliceName] = slice = Object.assign({}, slice);
-      slice["count"] = store.count("devices", filter);
+    charts[chartName] = chart = { ...chart };
+    chart.slices = chart.slices.map((s) => ({ ...s }));
+    for (const slice of chart.slices) {
+      slice["count"] = store.count("devices", slice.filter);
     }
   }
   return charts;
 }
 
-export function init(): Promise<Record<string, unknown>> {
+export function init(): Promise<{ charts: typeof overview.charts }> {
   if (!window.authorizer.hasAccess("devices", 1)) {
     return Promise.reject(
       new Error("You are not authorized to view this page"),
@@ -35,37 +33,36 @@ export function init(): Promise<Record<string, unknown>> {
   return Promise.resolve({ charts: queryCharts(CHARTS) });
 }
 
-export const component: ClosureComponent = (): Component => {
+interface Attrs {
+  charts: typeof overview.charts;
+}
+
+export const component: ClosureComponent<Attrs> = () => {
   return {
     view: (vnode) => {
       document.title = "Overview - GenieACS";
       const children = [];
-      for (const group of Object.values(GROUPS)) {
-        if (group["label"]) {
+      for (const group of GROUPS) {
+        if (group.label) {
           children.push(
-            m(
-              "h1.text-xl font-medium text-stone-900 mb-5",
-              store.evaluateExpression(group["label"], null),
-            ),
+            m("h1.text-xl font-medium text-stone-900 mb-5", group["label"]),
           );
         }
 
         const groupChildren = [];
-        for (const chartName of Object.values(group["charts"]) as string[]) {
-          const chart = vnode.attrs["charts"][chartName];
+        for (const chartName of group.charts) {
+          const chart = vnode.attrs.charts[chartName];
           const chartChildren = [];
           if (chart.label) {
             chartChildren.push(
               m(
                 "h2.text-lg font-semibold text-stone-700 truncate mb-5 text-center",
-                store.evaluateExpression(chart.label, null),
+                chart.label,
               ),
             );
           }
 
-          const attrs = {};
-          attrs["chart"] = chart;
-          chartChildren.push(m(pieChartComponent, attrs));
+          chartChildren.push(m(pieChartComponent, { chart }));
 
           groupChildren.push(
             m(