Add duplicate approval flow with time-based dedup

- expenses_agent: extract transaction time (HH:MM) from OCR receipt text
- expenses_agent: _find_semantic_duplicate uses time to rule out false positives (>30 min apart = different receipts)
- expenses_agent: pause when duplicates found, set mode=awaiting_dup_approval, ask user before creating sheet
- expenses_agent: _report formats approval message listing each dup pair with vendor/amount/date/times/filenames
- ab_ai_mail: _find_pending_attachments recognises dup-approval bot message so ZIP re-attaches on user reply

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

addons/activeblue_ai/models/ab_ai_mail.py

@@ -191,12 +191,18 @@ class DiscussChannel(models.Model):
         (i.e. the bot hasn't already acted on those files).
         """
         messages = self.message_ids.sorted('date', reverse=True)[:_LOOKBACK_MESSAGES]
+        _bot_question_phrases = (
+            'what would you like me to do',
+            'suspected duplicate',
+            'skip duplicates',
+            'keep all',
+        )
         prev_was_bot_question = False
         for msg in messages:
             is_bot = msg.author_id == bot_partner
             if is_bot:
-                # Check whether this bot message was a clarification question
-                if 'what would you like me to do' in (msg.body or '').lower():
+                body_lower = (msg.body or '').lower()
+                if any(p in body_lower for p in _bot_question_phrases):
                     prev_was_bot_question = True
                 continue
             # Human message