Add progressive web app companion for cross-platform access

Vite + TypeScript PWA that mirrors the Android app's core features:
- Pre-processed shelter data (build-time UTM33N→WGS84 conversion)
- Leaflet map with shelter markers, user location, and offline tiles
- Canvas compass arrow (ported from DirectionArrowView.kt)
- IndexedDB shelter cache with 7-day staleness check
- Service worker with CacheFirst tiles and precached app shell
- i18n for en, nb, nn (ported from Android strings.xml)
- iOS/Android compass handling with low-pass filter
- Respects user map interaction (no auto-snap on pan/zoom)
- Build revision cache-breaker for reliable SW updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pwa/node_modules/ajv/lib/refs/json-schema-2020-12/meta/validation.json

@@ -0,0 +1,90 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://json-schema.org/draft/2020-12/meta/validation",
+  "$vocabulary": {
+    "https://json-schema.org/draft/2020-12/vocab/validation": true
+  },
+  "$dynamicAnchor": "meta",
+
+  "title": "Validation vocabulary meta-schema",
+  "type": ["object", "boolean"],
+  "properties": {
+    "type": {
+      "anyOf": [
+        {"$ref": "#/$defs/simpleTypes"},
+        {
+          "type": "array",
+          "items": {"$ref": "#/$defs/simpleTypes"},
+          "minItems": 1,
+          "uniqueItems": true
+        }
+      ]
+    },
+    "const": true,
+    "enum": {
+      "type": "array",
+      "items": true
+    },
+    "multipleOf": {
+      "type": "number",
+      "exclusiveMinimum": 0
+    },
+    "maximum": {
+      "type": "number"
+    },
+    "exclusiveMaximum": {
+      "type": "number"
+    },
+    "minimum": {
+      "type": "number"
+    },
+    "exclusiveMinimum": {
+      "type": "number"
+    },
+    "maxLength": {"$ref": "#/$defs/nonNegativeInteger"},
+    "minLength": {"$ref": "#/$defs/nonNegativeIntegerDefault0"},
+    "pattern": {
+      "type": "string",
+      "format": "regex"
+    },
+    "maxItems": {"$ref": "#/$defs/nonNegativeInteger"},
+    "minItems": {"$ref": "#/$defs/nonNegativeIntegerDefault0"},
+    "uniqueItems": {
+      "type": "boolean",
+      "default": false
+    },
+    "maxContains": {"$ref": "#/$defs/nonNegativeInteger"},
+    "minContains": {
+      "$ref": "#/$defs/nonNegativeInteger",
+      "default": 1
+    },
+    "maxProperties": {"$ref": "#/$defs/nonNegativeInteger"},
+    "minProperties": {"$ref": "#/$defs/nonNegativeIntegerDefault0"},
+    "required": {"$ref": "#/$defs/stringArray"},
+    "dependentRequired": {
+      "type": "object",
+      "additionalProperties": {
+        "$ref": "#/$defs/stringArray"
+      }
+    }
+  },
+  "$defs": {
+    "nonNegativeInteger": {
+      "type": "integer",
+      "minimum": 0
+    },
+    "nonNegativeIntegerDefault0": {
+      "$ref": "#/$defs/nonNegativeInteger",
+      "default": 0
+    },
+    "simpleTypes": {
+      "enum": ["array", "boolean", "integer", "null", "number", "object", "string"]
+    },
+    "stringArray": {
+      "type": "array",
+      "items": {"type": "string"},
+      "uniqueItems": true,
+      "default": []
+    }
+  }
+}