feat: add price screener with SQLite caching and refactor codebase

[HanSoBored]

Summary

• Add Price Screener — New cryptoscope screener subcommand with SQLite-backed open price caching, concurrent kline/ticker fetching, and formatted terminal output with color-coded gainers/losers
• Add Database Layer — SQLite with schema migrations, connection pooling, and UPSERT semantics for open price storage
• Refactor Codebase — Replace struct-based modules (TextFormatter, CyberdeckTheme, InstrumentFetcher, TuiApp) with idiomatic free functions
• Add CLI Subcommands — Restructured CLI with screener subcommand, CommonArgs struct, and --exchange flag
• Improve TUI — Extract LogGuard RAII struct, add popup messages, clickable header tabs, and mouse support
• Update README — Document screener feature, all CLI flags, TUI interactions, and fix outdated paths

Changes

New Features

• cryptoscope screener — Price screener with DB caching (kline & ticker modes)
• --exchange / -e flag for exchange selection
• --symbol filter for screener output
• SQLite database with automatic migrations
• TUI popup messages (5s timeout, dismissible)
• Clickable header tabs in TUI

Refactoring

• TextFormatter → free functions (src/output/)
• CyberdeckTheme → module constants (src/tui/theme.rs)
• InstrumentFetcher → free functions (src/fetcher/)
• TuiApp → TuiLifecycle + LogGuard (src/tui/runner.rs)
• HasCategory trait → parse_categories_from() free function
• Arc<Mutex<usize>> → AtomicUsize for counters
• INSERT OR REPLACE → ON CONFLICT DO UPDATE for true upsert

Code Quality

• Deterministic JSON serialization (sorted keys)
• True concurrent streaming (mpsc channel + semaphore)
• Bounds-safe parse_kline_field with .get(idx)
• Single-pass .fold() for group statistics
• Added WHY comments for complex logic

Commits

#	Commit	Description
1	feat(db)	SQLite database layer with migration support
2	feat(utils)	Logging system, shared utilities, test helpers
3	feat(screener)	Price fetcher with concurrent kline fetching
4	feat(screener)	Screener orchestration and calculator
5	refactor(cli)	Subcommands, CommonArgs, error handling
6	refactor(exchange)	Simplify bybit client, free functions
7	refactor(models)	Response types, deterministic serialization
8	refactor(output)	Replace TextFormatter with free functions
9	refactor(tui)	TuiLifecycle, LogGuard, theme constants
10	refactor(tui)	Widgets, sorted stats, popup messages
11	docs	README update with screener and new flags

Verification

• Build: ✅ Pass
• Lint (clippy): ✅ Pass
• Tests: ✅ Pass (57/57)

[HanSoBored]

LGTM, needs Update README

[HanSoBored]

Merge!