Add verse progress checkboxes, chapter audio playback, and reading mode

[Copilot]

Three new interactive features for the Quran reader, requested for improved reading/tracking UX.

Verse Progress Checkboxes (☑️)

• Per-verse checkbox on every ayah-sep row — manually tick to mark progress
• Chapter-level "All Read" checkbox in the H1 bar — marks/unmarks all verses at once
• State persisted per-surah in localStorage (quran-prog-{sura}, JSON array of read ayah numbers)
• Auto-ticked when chapter audio finishes a verse (markAyahReadAuto)
• Read verses get a green background on the separator row (.ayah-sep.ayah-read)

Chapter-Level Audio Play (▶️)

• "▶ Play Chapter" button beside the chapter title — plays all per-verse Alafasy MP3s sequentially
• Scrolls to each verse as it plays; auto-checks verse checkbox on completion
• Toggles to "⏸ Stop" while active

Reading Mode (📚)

• Toggle button in the H1 bar; state persisted in localStorage (quran-rm)
• When active: non-current rows dimmed to 25% opacity; current verse (tracked at ~38% viewport height on scroll) at 100% with a gold left border; scrolled-past verses at 50%

Implementation

All logic lives in src/gendocshtml.py — three new JS IIFEs appended to VC_JS, new CSS classes added to the CSS constant, and HEADER_HTML updated to wrap <h1> in a .h1-controls flex container. All 114 surah HTML files regenerated.

Screenshots

Default view — chapter controls and per-verse checkboxes:

Verse 1 marked as read (green row):

Reading Mode active — non-current verses dimmed:

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