docs: improve Entity-Linking documentation

[Flo0806]

Summary

The landing page documentation needs updates to match the current app features.

Changes needed

Entity-Linking Section (done)

• Clarify that IDs are used internally ({{npc:42}}), not names
• Document the Quick-Insert flow with Ctrl+Space / Cmd+Space
• Add step-by-step example showing the popup workflow
• Document type shortcuts (npc, loc, item, fac, lore, player, ses)
• Document toolbar buttons as alternative method
• Mention legacy format support ([Name](type:id))

Keyboard Shortcuts Section (done)

• Split into "Global" and "In Text Editor" sections
• Add Ctrl+Space / Cmd+Space for Quick-Insert
• Add navigation shortcuts (↑/↓, Tab, Enter, Esc)

NEW: Dashboard Section (missing)

• Add dedicated Dashboard section
• Document Stats-Widget (playtime, session count, entity count, pinned count)
• Document Calendar-Widget (current in-game date, days since first session)
• Document Notes-Widget (recent notes with pending count)
• Document Pinboard-Widget (pinned entities with quick preview)
• Document Maps-Widget (map preview with marker count)
• Document responsive layout behavior

NEW: 3D Dice Animation (missing)

• Document dice rolling feature on dashboard
• Auto-roll 2d20 on page load
• Click to re-roll
• Rust theme with DM Hero gold color

NEW: Update Checker - Electron only (missing)

• Document auto-update notification system
• Banner in NavigationDrawer when update available
• Link to GitHub releases for download

NEW: Copy to Campaign (needs clarification)

• Clarify workflow and where to access this feature
• Explain difference from export/import

Files affected

• packages/landing/content/docs/3.features.md (English)
• packages/landing/content/docs/de/3.features.md (German)

Progress

Entity-Linking and Keyboard Shortcuts changes are already implemented locally.