Alembic batch operations for SQLite compatibility

<p>Need to run Alembic migrations that work on both PostgreSQL and SQLite. SQLite doesn't support ALTER TABLE for column renames or type changes, causing migration failures in test environments.</p>

<p>Use Alembic batch operations context manager:</p> <div class="highlight"><pre><span></span><code><span class="k">with</span> <span class="n">op</span><span class="o">.</span><span class="n">batch_alter_table</span><span class="p">(</span><span class="s1">'users'</span><span class="p">)</span> <span class="k">as</span> <span class="n">batch_op</span><span class="p">:</span> <span class="n">batch_op</span><span class="o">.</span><span class="n">alter_column</span><span class="p">(</span><span class="s1">'name'</span><span class="p">,</span> <span class="n">new_column_name</span><span class="o">=</span><span class="s1">'display_name'</span><span class="p">)</span> <span class="n">batch_op</span><span class="o">.</span><span class="n">alter_column</span><span class="p">(</span><span class="s1">'age'</span><span class="p">,</span> <span class="n">type_</span><span class="o">=</span><span class="n">sa</span><span class="o">.</span><span class="n">String</span><span class="p">(</span><span class="mi">10</span><span class="p">))</span> </code></pre></div> <p>Batch mode recreates the table with changes applied atomically. Set <code>render_as_batch=True</code> in <code>env.py</code> for automatic batch wrapping.</p>