Fix TypeError when revision_count is stored as TEXT

The previous schema migration added revision_count as TEXT. SQLite stores
the default as TEXT, but the app does integer arithmetic on it, causing:

  TypeError: unsupported operand type(s) for -: 'int' and 'str'

- init_db() now adds revision_count as INTEGER.
- app.py casts revision_count to int in play() and revise() and when
  incrementing in revise(), so existing TEXT values also work.

Bump version 0.4.2 -> 0.4.3.

app.py

@@ -621,7 +621,7 @@ def play(token):
 
     # Load runtime max revisions setting.
     max_revisions = get_max_revisions()
-    revisions_left = max(0, max_revisions - (req.get('revision_count') or 0))
+    revisions_left = max(0, max_revisions - int(req.get('revision_count') or 0))
 
     return render_template('player.html', req=req, revisions_left=revisions_left)
 
@@ -661,7 +661,7 @@ def revise(token):
 
     # Enforce max revisions limit for customer-submitted revisions.
     max_revisions = get_max_revisions()
-    current_count = req.get('revision_count') or 0
+    current_count = int(req.get('revision_count') or 0)
     if current_count >= max_revisions:
         flash('Revision limit reached. Please speak to the booth operator if you need further changes.', 'error')
         return redirect(url_for('play', token=token))
@@ -689,7 +689,7 @@ def revise(token):
     log_revision(req['id'], new_count, note, old_a=old_a, old_b=old_b, new_a=new_a, new_b=new_b)
     update_request(req['id'], revision_note=note, status='revisions_requested',
                    song_a_path=req.get('song_a_path'), song_b_path=req.get('song_b_path'),
-                   customer_approved='none', revision_count=new_count)
+                   customer_approved='none', revision_count=int(new_count))
 
     # NOTE: No operator email is sent; the dashboard is the single queue.
     flash('Your feedback has been saved. We will regenerate and update you.', 'success')