fix(deploy): allow picking an existing photo, not just camera capture

The photo input had `capture="environment"` which forces mobile
browsers to open the camera and skip the "Photo Library" / "Choose
File" options.  Useful when you're literally at the install site,
problematic when you took the photo earlier and want to upload it
now from your gallery.

Removed the attribute.  Most mobile browsers now present a chooser
("Take Photo", "Photo Library", "Choose File").  EXIF extraction works
identically either way — the server doesn't care whether the file came
from the camera or the gallery.

Hint copy updated to reflect both options.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

templates/deploy.html

@@ -53,11 +53,11 @@
 
         <label class="block">
             <span class="text-sm font-medium text-gray-700 dark:text-gray-300">Install photo</span>
-            <input id="photo-input" type="file" accept="image/*" capture="environment"
+            <input id="photo-input" type="file" accept="image/*"
                    onchange="onPhotoPicked(event)"
                    class="mt-2 w-full text-sm text-gray-500 file:mr-4 file:py-3 file:px-4 file:rounded-lg file:border-0 file:text-sm file:font-semibold file:bg-seismo-orange file:text-white hover:file:bg-orange-600">
             <p class="text-xs text-gray-500 dark:text-gray-400 mt-1">
-                On mobile, this opens the camera.  EXIF GPS is auto-extracted.
+                Take a new photo or pick a previously taken one.  EXIF GPS is auto-extracted either way.
             </p>
         </label>