Implement Barrikade security client and pluggable framework

[Ishaan005]

Description

This PR introduces a Security Plugin Registry to jentic-mini's gateway and integrates Barrikade as the primary security plugin.

Instead of hardcoding security logic or relying on redundant, high-latency request-body scans at the egress broker layer (which are already captured by the global SecurityIngressMiddleware at ingress), jentic-mini now implements a modular registry interface that intercepts and scans API response bodies returned by third-party services. This provides critical protection against data leaks, PII exfiltration, and indirect prompt injections before they reach the agent or Arazzo workflow runner.

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Architectural Refactor

                  ┌───────────────────────────┐
                  │   Inbound Client Request  │
                  └─────────────┬─────────────┘
                                │
                                ▼
              ┌───────────────────────────────────┐
              │     SecurityIngressMiddleware     │
              └─────────────────┬─────────────────┘
                                │ (scan_ingress)
                                ▼
              ┌───────────────────────────────────┐
              │      security_registry (SL)       │
              └─────────────────┬─────────────────┘
                                │
                    ┌───────────┴───────────┐
                    ▼                       ▼
         ┌─────────────────────┐ ┌─────────────────────┐
         │   BarrikadePlugin   │ │   CustomPlugin      │
         └──────────┬──────────┘ └──────────┬──────────┘
                    │                       │
                    ▼ (scan_text)           ▼
         ┌─────────────────────-┐ ┌─────────────────────-┐
         │ Barrikade API /detect│ │   Custom Classifier  │       
         └─────────────────────-┘ └─────────────────────-┘

1. Ingress Boundary (Middleware): Scans query parameters and inbound payloads (POST/PUT/etc.) using security_registry.scan_ingress before routing or database execution.
2. Egress Boundary (Response): Intercepts raw responses inside broker.py right after _upstream_body = await upstream_response.read() and scans them via security_registry.scan_response before delivery.

---

Summary of Changes

1. Security Registry & Interfaces (src/security/)

• src/security/plugin.py:
  • Declares slotted SecurityVerdict for lightweight, high-performance classifications.
  • Declares SecurityPlugin abstract base class with default ingress filter (should_scan_ingress), response filter (should_scan_response), and delegating scan_response methods.
• src/security/registry.py:
  • Implements SecurityRegistry singleton coordinating active plugins.
  • Employs first-block-wins short-circuiting on active scans to optimize Latency and prevent redundant operations.
• src/security/barrikade.py:
  • Concrete SecurityPlugin subclassing SecurityPlugin. Encapsulates direct HTTP calls to Barrikade’s stateless /v1/detect API.
  • Overrides should_scan_ingress to target only Jentic’s /search, /workflows/{slug}, and broker routing paths.
• src/security/utils.py:
  • High-performance, isolated text extraction algorithms that recursively traverse nested JSON list/dict query strings and request/response payloads to isolate raw strings.

2. Router Integration (src/routers/)

• src/routers/broker.py:
  • Completely removed the old, redundant request-egress security block (cutting outbound proxying latency in half).
  • Added response-body scanning directly after upstream reading is complete. Unsafe responses instantly trigger a policy_denied trace and short-circuit with a structured 403 Forbidden response-block verdict.
• src/main.py:
  • Configured SecurityIngressMiddleware to delegate directly to security_registry without carrying any vendor-specific imports.
  • Registers BarrikadePlugin dynamically in lifespan if BARRIKADE_URL is set in the environment.

3. Tooling & Orchestration

• compose.barrikade.yml: Added a new Docker Compose stack configuration file overlaying compose.yml to define the local barrikade/api service and link it to Jentic Mini internally.
• scripts/start-stack.sh: Created an interactive shell script to spin up the Jentic Mini + Barrikade containers (Standard or Full Vite UI Dev stack) instantly.
• docs/security.md: Created exhaustive system design, lifecycle, configuration, and custom plugin development documentation, linked in docs/README.md.

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This change requires real-world testing with live APIs. The foundation is in place and should be reiterated on.