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

package.json

@@ -38,7 +38,6 @@
     "koa-jwt": "^4.0.3",
     "koa-send": "^5.0.1",
     "mongodb": "^4.16.0",
-    "parsimmon": "^1.18.1",
     "seedrandom": "^3.0.5"
   },
   "devDependencies": {
@@ -56,7 +55,6 @@
     "@types/koa-compress": "^4.0.7",
     "@types/mithril": "^2.2.7",
     "@types/node": "^25.3.5",
-    "@types/parsimmon": "^1.10.9",
     "@types/seedrandom": "^3.0.8",
     "esbuild": "^0.27.4",
     "eslint": "^10.0.3",