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/ui-config-component.ts

@@ -4,7 +4,7 @@ import * as store from "./store.ts";
 import { yaml } from "./dynamic-loader.ts";
 import * as configFunctions from "./config-functions.ts";
 import codeEditorComponent from "./code-editor-component.ts";
-import { parse } from "../lib/common/expression/parser.ts";
+import Expression from "../lib/common/expression.ts";
 
 function putActionHandler(prefix: string[], dataYaml: string): Promise<any> {
   return new Promise((resolve, reject) => {
@@ -27,7 +27,7 @@ function putActionHandler(prefix: string[], dataYaml: string): Promise<any> {
       }
 
       // Try parse to ensure valid expressions
-      for (const v of Object.values(updated)) parse(v as string);
+      for (const v of Object.values(updated)) Expression.parse(v as string);
 
       store
         .queryConfig(`${prefix.join(".")}.%`)