Add startup progress logging and banner display to ft-executor

[Copilot]

Fixes #24 by adding comprehensive startup progress logging and banner display to ft-executor, bringing it in line with ft-timeoracle for improved usability and observability.

Changes Made

Startup Progress Logging

Added detailed logging throughout the startup process in ft-executor/main.go:

• Initial startup message with version and process ID
• Configuration loading progress notifications
• Database connection establishment logging
• Time source oracle creation confirmation
• Server initialization details with key parameters

Banner Display

The existing ASCII banner (which was defined but never displayed) is now shown after successful initialization, providing clear visual confirmation that the executor is ready.

Example Output

When running with LOG=INFO, users now see a clear startup sequence:

2025-08-11T07:13:25Z	INFO	ft-executor/main.go:584	Starting Oreo Executor	{"version": "1.0", "pid": 8315}
2025-08-11T07:13:25Z	INFO	ft-executor/main.go:587	Loading benchmark configuration...
2025-08-11T07:13:25Z	INFO	ft-executor/main.go:598	Benchmark configuration loaded successfully	{"config_path": "/tmp/test-config.yaml"}
2025-08-11T07:13:25Z	INFO	ft-executor/main.go:632	Establishing database connections...	{"workload": "iot", "db_combination": ""}
2025-08-11T07:13:25Z	INFO	ft-executor/main.go:665	Creating time source oracle	{"oracle_url": "http://localhost:8012/timestamp/common"}
2025-08-11T07:13:25Z	INFO	ft-executor/main.go:669	Creating executor server	{"port": 8000, "advertise_addr": "localhost:8000", "registry_addr": "http://localhost:9000", "registry_type": "http"}

 ____  _        _       _               
/ ___|| |_ __ _| |_ ___| | ___  ___ ___ 
\___ \| __/ _| | __/ _ \ |/ _ \/ __/ __|
 ___) | || (_| | ||  __/ |  __/\__ \__ \
|____/ \__\__,_|\__\___|_|\___||___/___/
2025-08-11T07:13:25Z	INFO	ft-executor/main.go:688	Oreo Executor initialized successfully

Implementation Details

• Minimal changes: Only 20 lines added, focusing on logging statements and banner display
• Consistent patterns: Follows the same structured logging approach used in ft-timeoracle
• Backward compatibility: No breaking changes to existing functionality
• Structured logging: Uses key-value pairs for better log parsing and observability

The implementation improves the developer and operator experience by providing clear visibility into the startup process, making it easier to debug issues and confirm successful initialization.

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