Add keyboard-shortcuts.html docs page

[RasputinKaiser]

Summary

New standalone docs page documenting every StorageScope keyboard shortcut shipped in v0.4.5 plus a "Coming in v0.5.0" section.

Covers:

• Default shortcuts table (Cmd+F / Cmd+W / Cmd+Ctrl+F / Cmd+, / Cmd+R / Cmd+. / Cmd+O / Cmd+Shift+H/D/L / Cmd+Shift+F / Cmd+Option+C / Cmd+Delete / Cmd+Enter / Cmd+A / Cmd+C/V/X / Cmd+M / Cmd+N / Cmd+Q)
• Smart View hotkeys Cmd+1-8 mirroring SmartView.allCases order (Overview / Cleanup Review / Folder Tree / Largest Folders / Largest Files / Old Large Files / File Types / Duplicate Review)
• "Coming in v0.5.0" section previewing Cmd+G / Cmd+Shift+G find-next navigation
• Notes section explaining modifier keys + Find-on-macOS-14 fallback behavior

Page structure mirrors existing docs/index.html: inline <style> with :root CSS variables + @media (prefers-color-scheme: dark), shared <header class="site-nav"> block, interactive <kbd> styling for shortcuts. Footer banner at v0.4.5.

Test plan

• HTML parses cleanly via python3 HTMLParser().feed(...)
• Smart View ordering matches Sources/StorageScope/Stores/SmartView.swift allCases order
• swift test passes (54 tests in 5 suites)
• swift build succeeds
• ./script/public_upload_audit.sh passes
• Light + dark mode rendering verified
• No occurrence of surname "Zvirbulis"; uses GitHub handle "RasputinKaiser"

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