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

workers/rust/Dockerfile

@@ -0,0 +1,85 @@
+# FuzzForge Vertical Worker: Rust/Native Security
+#
+# Pre-installed tools for Rust and native binary security analysis:
+# - Rust toolchain (rustc, cargo)
+# - AFL++ (fuzzing)
+# - cargo-fuzz (Rust fuzzing)
+# - gdb (debugging)
+# - valgrind (memory analysis)
+# - AddressSanitizer/MemorySanitizer support
+# - Common reverse engineering tools
+
+FROM rust:1.83-slim-bookworm
+
+# Set working directory
+WORKDIR /app
+
+# Install system dependencies
+RUN apt-get update && apt-get install -y \
+    # Build essentials
+    build-essential \
+    cmake \
+    git \
+    curl \
+    wget \
+    pkg-config \
+    libssl-dev \
+    # AFL++ dependencies
+    clang \
+    llvm \
+    # Debugging and analysis tools
+    gdb \
+    valgrind \
+    strace \
+    # Binary analysis (binutils includes objdump, readelf, etc.)
+    binutils \
+    # Network tools
+    netcat-openbsd \
+    tcpdump \
+    # Python for Temporal worker
+    python3 \
+    python3-pip \
+    python3-venv \
+    # Cleanup
+    && rm -rf /var/lib/apt/lists/*
+
+# Install AFL++
+RUN git clone https://github.com/AFLplusplus/AFLplusplus /tmp/aflplusplus && \
+    cd /tmp/aflplusplus && \
+    make all && \
+    make install && \
+    cd / && \
+    rm -rf /tmp/aflplusplus
+
+# Install Rust toolchain components
+RUN rustup component add rustfmt clippy && \
+    rustup target add x86_64-unknown-linux-musl
+
+# Install cargo-fuzz and other Rust security tools
+RUN cargo install --locked \
+    cargo-fuzz \
+    cargo-audit \
+    cargo-outdated \
+    cargo-tree
+
+# Install Python dependencies for Temporal worker
+COPY requirements.txt /tmp/requirements.txt
+RUN pip3 install --break-system-packages --no-cache-dir -r /tmp/requirements.txt && \
+    rm /tmp/requirements.txt
+
+# Create cache directory for downloaded targets
+RUN mkdir -p /cache && chmod 755 /cache
+
+# Copy worker entrypoint
+COPY worker.py /app/worker.py
+
+# Add toolbox to Python path (mounted at runtime)
+ENV PYTHONPATH="/app:/app/toolbox:${PYTHONPATH}"
+ENV PYTHONUNBUFFERED=1
+
+# Healthcheck
+HEALTHCHECK --interval=30s --timeout=10s --start-period=40s --retries=3 \
+    CMD python3 -c "import sys; sys.exit(0)"
+
+# Run worker
+CMD ["python3", "/app/worker.py"]