feat(bot): support concurrent drafts and reply-based edits with error resilience

backend/app/db/init_db.py

@@ -445,6 +445,7 @@ async def ensure_bot_drafts_table(engine: AsyncEngine) -> None:
         missing             JSONB,
         status              VARCHAR(16) NOT NULL DEFAULT 'active',
         source              VARCHAR(16),
+        source_message_id   BIGINT,
         review_message_id   BIGINT,
         last_bale_update_at TIMESTAMPTZ,
         created_at          TIMESTAMPTZ NOT NULL DEFAULT now(),
@@ -455,6 +456,9 @@ async def ensure_bot_drafts_table(engine: AsyncEngine) -> None:
         "CREATE INDEX IF NOT EXISTS ix_bot_drafts_chat_id ON bot_drafts(chat_id)",
         "CREATE INDEX IF NOT EXISTS ix_bot_drafts_chat_status ON bot_drafts(chat_id, status)",
         "ALTER TABLE bot_drafts ADD COLUMN IF NOT EXISTS last_bale_update_at TIMESTAMPTZ",
+        "ALTER TABLE bot_drafts ADD COLUMN IF NOT EXISTS source_message_id BIGINT",
+        "CREATE INDEX IF NOT EXISTS ix_bot_drafts_review_msg ON bot_drafts(review_message_id)",
+        "CREATE INDEX IF NOT EXISTS ix_bot_drafts_source_msg ON bot_drafts(source_message_id)",
     )
     async with engine.begin() as conn:
         await conn.execute(text(ddl))

backend/app/models/draft.py

@@ -14,6 +14,7 @@ class BotDraft(Base):
     missing = Column(JSONB)
     status = Column(String(16), nullable=False, default="active")
     source = Column(String(16))
+    source_message_id = Column(BigInteger)
     review_message_id = Column(BigInteger)
     last_bale_update_at = Column(DateTime(timezone=True))
     created_at = Column(DateTime(timezone=True), server_default=func.now())