feat: Complete migration from Prefect to Temporal

BREAKING CHANGE: Replaces Prefect workflow orchestration with Temporal

## Major Changes
- Replace Prefect with Temporal for workflow orchestration
- Implement vertical worker architecture (rust, android)
- Replace Docker registry with MinIO for unified storage
- Refactor activities to be co-located with workflows
- Update all API endpoints for Temporal compatibility

## Infrastructure
- New: docker-compose.temporal.yaml (Temporal + MinIO + workers)
- New: workers/ directory with rust and android vertical workers
- New: backend/src/temporal/ (manager, discovery)
- New: backend/src/storage/ (S3-cached storage with MinIO)
- New: backend/toolbox/common/ (shared storage activities)
- Deleted: docker-compose.yaml (old Prefect setup)
- Deleted: backend/src/core/prefect_manager.py
- Deleted: backend/src/services/prefect_stats_monitor.py
- Deleted: Docker registry and insecure-registries requirement

## Workflows
- Migrated: security_assessment workflow to Temporal
- New: rust_test workflow (example/test workflow)
- Deleted: secret_detection_scan (Prefect-based, to be reimplemented)
- Activities now co-located with workflows for independent testing

## API Changes
- Updated: backend/src/api/workflows.py (Temporal submission)
- Updated: backend/src/api/runs.py (Temporal status/results)
- Updated: backend/src/main.py (727 lines, TemporalManager integration)
- Updated: All 16 MCP tools to use TemporalManager

## Testing
- ✅ All services healthy (Temporal, PostgreSQL, MinIO, workers, backend)
- ✅ All API endpoints functional
- ✅ End-to-end workflow test passed (72 findings from vulnerable_app)
- ✅ MinIO storage integration working (target upload/download, results)
- ✅ Worker activity discovery working (6 activities registered)
- ✅ Tarball extraction working
- ✅ SARIF report generation working

## Documentation
- ARCHITECTURE.md: Complete Temporal architecture documentation
- QUICKSTART_TEMPORAL.md: Getting started guide
- MIGRATION_DECISION.md: Why we chose Temporal over Prefect
- IMPLEMENTATION_STATUS.md: Migration progress tracking
- workers/README.md: Worker development guide

## Dependencies
- Added: temporalio>=1.6.0
- Added: boto3>=1.34.0 (MinIO S3 client)
- Removed: prefect>=3.4.18

backend/tests/test_prefect_stats_monitor.py

@@ -1,82 +0,0 @@
-# Copyright (c) 2025 FuzzingLabs
-#
-# Licensed under the Business Source License 1.1 (BSL). See the LICENSE file
-# at the root of this repository for details.
-#
-# After the Change Date (four years from publication), this version of the
-# Licensed Work will be made available under the Apache License, Version 2.0.
-# See the LICENSE-APACHE file or http://www.apache.org/licenses/LICENSE-2.0
-#
-# Additional attribution and requirements are provided in the NOTICE file.
-
-import asyncio
-from datetime import datetime, timezone, timedelta
-
-
-from src.services.prefect_stats_monitor import PrefectStatsMonitor
-from src.api import fuzzing
-
-
-class FakeLog:
-    def __init__(self, message: str):
-        self.message = message
-
-
-class FakeClient:
-    def __init__(self, logs):
-        self._logs = logs
-
-    async def read_logs(self, log_filter=None, limit=100, sort="TIMESTAMP_ASC"):
-        return self._logs
-
-
-class FakeTaskRun:
-    def __init__(self):
-        self.id = "task-1"
-        self.start_time = datetime.now(timezone.utc) - timedelta(seconds=5)
-
-
-def test_parse_stats_from_log_fuzzing():
-    mon = PrefectStatsMonitor()
-    msg = (
-        "INFO LIVE_STATS extra={'stats_type': 'fuzzing_live_update', "
-        "'executions': 42, 'executions_per_sec': 3.14, 'crashes': 1, 'unique_crashes': 1, 'corpus_size': 9}"
-    )
-    stats = mon._parse_stats_from_log(msg)
-    assert stats is not None
-    assert stats["stats_type"] == "fuzzing_live_update"
-    assert stats["executions"] == 42
-
-
-def test_extract_stats_updates_and_broadcasts():
-    mon = PrefectStatsMonitor()
-    run_id = "run-123"
-    workflow = "wf"
-    fuzzing.initialize_fuzzing_tracking(run_id, workflow)
-
-    # Prepare a fake websocket to capture messages
-    sent = []
-
-    class FakeWS:
-        async def send_text(self, text: str):
-            sent.append(text)
-
-    fuzzing.active_connections[run_id] = [FakeWS()]
-
-    # Craft a log line the parser understands
-    msg = (
-        "INFO LIVE_STATS extra={'stats_type': 'fuzzing_live_update', "
-        "'executions': 10, 'executions_per_sec': 1.5, 'crashes': 0, 'unique_crashes': 0, 'corpus_size': 2}"
-    )
-    fake_client = FakeClient([FakeLog(msg)])
-    task_run = FakeTaskRun()
-
-    asyncio.run(mon._extract_stats_from_task(fake_client, run_id, task_run, workflow))
-
-    # Verify stats updated
-    stats = fuzzing.fuzzing_stats[run_id]
-    assert stats.executions == 10
-    assert stats.executions_per_sec == 1.5
-
-    # Verify a message was sent to WebSocket
-    assert sent, "Expected a stats_update message to be sent"