Add version picker to web flasher

Lets users choose among the last 3 releases (v3.6.3 latest, v3.6.2,
v3.6.1) instead of only ever flashing the newest build - handy for
testing or rolling back. Archives the real historical binaries for
v3.6.1/v3.6.2 under versions/, each with its own manifest.json.

Documents the archival step as part of the standard release workflow
in CLAUDE.md so the picker stays current on future releases.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

versions/v3.6.2/manifest.json

@@ -0,0 +1,14 @@
+{
+  "name": "Eiswolfs Flightradar (CYD)",
+  "new_install_prompt_erase": true,
+  "builds": [
+    {
+      "chipFamily": "ESP32",
+      "parts": [
+        { "path": "bootloader.bin", "offset": 4096 },
+        { "path": "partitions.bin", "offset": 32768 },
+        { "path": "firmware.bin", "offset": 65536 }
+      ]
+    }
+  ]
+}