[AZ-450] [AZ-451] [AZ-452] [AZ-454] Externalize URLs + accessors

Refactor batch 1 of 2 for the 01-testability-refactoring epic
(AZ-447). Minimal-surgical edits to make the UI's external
dependencies overridable for the test profiles in
_docs/02_document/tests/environment.md.

- AZ-450 (C03): tile URLs externalized to VITE_OSM_TILE_URL and
  VITE_ESRI_TILE_URL with the production strings as defaults.
  Fixes the AC-N3 / NFT-RES-03 air-gap regression and lets the
  e2e profile's tile-stub serve tiles deterministically.
- AZ-451 (C04): Leaflet marker icon imported from the pinned
  leaflet package as a Vite asset; removes the unpkg.com CDN
  reference (also fixes the leaflet@1.7.1 vs ^1.9.4 mismatch).
- AZ-452 (C05): getApiBase() accessor reading
  VITE_API_BASE_URL. request(), refreshToken(), and createSSE()
  prepend the prefix. Default '' preserves every call site.
- AZ-454 (C07): JSDoc on setToken/getToken documenting the
  test-override intent so future cleanup doesn't delete them.

Also: .env.example documents every VITE_* var; vite-env.d.ts
declares ImportMetaEnv; .gitignore now excludes /dist and
*.tsbuildinfo (tracked-by-mistake cache file removed).

Build verification: `bunx tsc -b --noEmit` passes. No tests in
this run (testability-run exemption per refactor SKILL — tests
land in autodev Step 6).

Co-authored-by: Cursor <cursoragent@cursor.com>

src/vite-env.d.ts

@@ -2,3 +2,15 @@
 
 declare module '*.css'
 declare module 'leaflet-polylinedecorator'
+
+interface ImportMetaEnv {
+  readonly VITE_API_BASE_URL?: string
+  readonly VITE_OWM_API_KEY?: string
+  readonly VITE_OWM_BASE_URL?: string
+  readonly VITE_OSM_TILE_URL?: string
+  readonly VITE_ESRI_TILE_URL?: string
+}
+
+interface ImportMeta {
+  readonly env: ImportMetaEnv
+}