[Aikido] Fix SQL injection bypass in asyncpg.executemany parameter extraction

[aikido-autofix]

This patch addresses a SQL injection vulnerability bypass in the asyncpg.executemany method where the security scanner was incorrectly extracting the query parameter instead of the command parameter, allowing malicious SQL to evade detection. A dedicated wrapper function _executemany was implemented to correctly identify and scan the command parameter for SQL injection attacks. The fix ensures proper vulnerability detection for batch query execution in asyncpg connections and includes comprehensive test coverage in aikido_zen/sinks/asyncpg.py and aikido_zen/sinks/tests/asyncpg_test.py.

✅ 1 issue fixed by this PR

Issue	Severity	Description
CodeAudit#811708154	HIGH	This is a protection-mechanism bypass in code within the audit scope. For an instrumented request handled in blocking mode, an application that incorporates request-controlled data into an asyncpg command can call connection.executemany(command=statement, args=rows). _execute requests query, so get_argument returns None; context_contains_sql_injection skips that value; and the wrapper proceeds to call the original method with the untouched arguments. No later check in this sink scans command. Consequently, SQL injection that this firewall is intended to detect and block can execute with the application's database role and evade the associated attack telemetry. The impact is conditional on an application endpoint constructing the command from attacker-influenced data, but that is the trust boundary the sink is intended to protect.