Add Go/TinyGo support, daemon shutdown, and log capture (#31)

[richardkiene]

Summary

This PR implements comprehensive Go/TinyGo support, graceful daemon shutdown, and per-service log capture functionality.

Go Builder

• Implemented GoBuilder using TinyGo 0.32+ with wasip2 target for WASI Preview 2 component generation
• Added toolchain verification for both TinyGo and wasm-tools
• Supports both command-line and HTTP service types
• Added working go-hello and go-http examples that build and run successfully

Daemon Shutdown

• Added fabricks daemon stop CLI command for graceful shutdown
• Implemented POST /v1/daemon/shutdown API endpoint
• Reduced shutdown timeout from 30s to 5s for faster termination
• Ensures clean service and resource cleanup on shutdown

Log Capture

• Implemented per-service bounded ring buffer (default: 10,000 lines)
• Captures stdout/stderr with timestamps and stream type differentiation
• Added fabricks service logs CLI command with -n/--tail flag
• Implemented GET /v1/services/:id/logs API endpoint
• Supports retrieval by both service ID and service name
• Provides both text and JSON output formats

Runtime Improvements

• Fixed critical bug: RuntimePool had fuel metering enabled but no fuel limit set, causing WASM to run out of fuel immediately
• Added default fuel limit of 10 billion when spawning instances
• Implemented LogCaptureSink and LogWriter for custom stdio capture
• Added run_with_output() method to Runtime for custom stdout/stderr handling
• Cleaned up excessive debug logging

Network Access

• Added auto-created "default" network with external access at daemon startup
• Made standalone services internal-only by default (secure by default)
• Requires explicit --network flag for external access
• Supports multiple networks via repeated --network flag

Documentation

• Updated architecture.md with log capture architecture and network design
• Updated cli-reference.md with daemon stop and service logs commands
• Updated daemon-api-reference.md with shutdown and logs API endpoints
• Documented network access patterns and security model

Test Plan

• Built and tested go-hello example (command-line service)
• Built and tested go-http example (HTTP service with health check)
• Verified daemon graceful shutdown with fabricks daemon stop
• Verified log capture for both stdout and stderr
• Tested log retrieval by service ID and name
• Verified network access with and without --network default
• Confirmed fuel limit fix resolves WASM execution issues
• Verified toolchain checks for TinyGo and wasm-tools

Related Issues

Closes #31