Security fixes: P0-P2 complete (22 fixes)

P0 (7): Auth-bypass removed, migrations fixed, plugin-upload disabled, RLS FORCE+WITH CHECK, plugin double-registration fixed, persistent volume, domain removed
P1 (11): User/tenant model, Redis centralized, worker separated, transactional outbox, XSS fixed, DMS chunked streaming, permissions unified, password reset, metrics secured, config/docs fixed, cross-tenant FK
P2 (4): Contact model normalized, cross-imports reduced 94%, commands+state machines for contacts/dms/mail/calendar, SPA path-traversal

8 new migrations, 99 unit tests, 13 commands, 8 contracts, 72 files changed

app/plugins/builtins/automation/agent_runner.py

@@ -191,7 +191,7 @@ async def run_agent(
 
             # Execute tool calls if LLM returned function calls
             if hasattr(response.choices[0].message, "tool_calls") and response.choices[0].message.tool_calls:
-                from app.plugins.builtins.ai_assistant.tool_registry import get_tool_registry
+                from app.plugins.builtins.ai_assistant.contracts import get_tool_registry
 
                 registry = get_tool_registry()
                 tool_call_count: dict[str, int] = {}