feat: add log file support and rendering optimisations

[neilmartin83]

Summary

Adds QuickLook preview support for log files (.log, .out, .err) with
heuristic-based syntax highlighting. Since log files have no consistent format,
the tokenizer uses pattern matching to colorize the most common elements that
make logs scannable at a glance.

Also speeds up rendering of large files.

What's highlighted

Element	Examples	Color
Timestamps	2025-09-16 06:20:56 +0100, Mar 28 14:05:33, Apache CLF	Muted (italic)
FATAL / CRITICAL / ALERT	FATAL, CRITICAL:	Bold red
ERROR	ERROR, ERROR:	Bold red
WARNING	WARN, WARNING:	Orange
INFO / NOTICE	INFO, INFO:	Blue
DEBUG / TRACE	DEBUG, VERBOSE	Muted (italic)
IPv4 addresses	192.168.1.100	Green
HTTP methods	GET, POST, DELETE	Purple
HTTP status codes	200 (green), 404 (orange), 500 (red)	By class
Double-quoted strings	"disk space low"	String color
File paths	/usr/local/etc/config.yaml	Variable color
Numbers with units	512MB, 30s, 94%	Green

Single quotes are intentionally not treated as string delimiters — apostrophes
in natural log text (JWT's, doesn't) are far too common.

Performance

Log files can be large (2MB+), so three optimizations were made:

• Line-by-line tokenization for .log — avoids O(n²) regex scanning over
  the entire file by processing each line independently
• escapeHTML rewritten as a single-pass character scan (was 4 chained
  replacingOccurrences calls, benefiting all formats)
• renderTokens uses a pre-allocated buffer instead of map + joined
• Truncation at ~500KB for all formats, with a
  "⋯ Preview truncated (X of Y lines shown)" notice

Files changed (8 files, +306 −23)

• Shared/SyntaxHighlighter.swift — .log format, tokenizer, perf improvements, truncation
• PiquePreview/Info.plist — UTI, QLSupportedContentTypes, QLFileExtensions
• PiquePreview/PreviewProvider.swift — format name mapping
• Pique/Info.plist — UTI declaration
• Pique/ContentView.swift — Log badge
• Pique/SettingsView.swift — Log in appearance settings
• PiqueTests/FileFormatTests.swift — extension mapping + case insensitivity
• PiqueTests/HighlightIntegrationTests.swift — 15 new tests

Tests

137 total, 0 failures. New tests cover:

• Severity levels (all tiers, with and without colon)
• Timestamps (ISO 8601, syslog)
• IPv4 addresses, HTTP methods, status code coloring by class
• File paths, double-quoted strings
• Apostrophe safety (JWT's not treated as string)
• Multi-line preservation
• Truncation for large inputs
• No truncation for small inputs
• Case-insensitive extension mapping (.LOG)