feat: UI cleanup and polish

[smagala]

Summary

• Update browser tab title from Vite default to "Voider - VOID Management Console"
• Move System Information panel to the top of the Dashboard
• Add "IDs Minted Today" card with backend minted_today field on /api/minter/statistics
• Align page content to top instead of vertically centered
• Remove redundant description from RequestBlock info card
• Sort block size dropdown smallest-to-largest
• Change pattern separator from / to . across RequestBlock and Statistics pages
• Rename "Shoulder Allocations" to "Block Allocations" in nav, page title, and dashboard heading
• Show combined shoulder.blade_pattern block identifier and add Capacity column in Allocations table
• Add external use flag to allocations with bidirectional guard against minter initialization
• PATCH endpoint for toggling external flag on allocations
• Allocations page enhancements: Purpose column, External toggle, Initialize Minter action with dialog
• Request Block form: external use checkbox
• 8 new backend tests covering external allocation scenarios

Closes #32, closes #33, closes #34, closes #35, closes #36, closes #37, closes #38, closes #39

Test plan

• yarn tsc --noEmit passes with no type errors
• yarn build completes successfully
• pytest passes all 104 backend tests (96 existing + 8 new)
• Browser tab shows "Voider - VOID Management Console"
• Dashboard: System Information panel appears at top of page
• Dashboard: "IDs Minted Today" card appears in ID Minting section
• All pages: content aligns to top, not vertically centered
• Request Block: no description text in Selected Block Info card
• Request Block: block sizes sorted smallest to largest in dropdown
• Request Block + Statistics: pattern shown as shoulder.blade (dot separator)
• Nav sidebar, Allocations page, Dashboard: "Block Allocations" label used
• Allocations table: Block column shows shoulder.blade_pattern, Capacity column present
• Hit /api/minter/statistics and confirm minted_today field is present
• Request Block form shows "External use" checkbox
• POST /api/authority/request with external: true returns external: true in response
• PATCH /api/authority/allocations/{id} with external: true toggles flag
• POST /api/minter/initialize for external allocation returns 403
• Allocations page: Purpose, External toggle, and Actions columns visible
• Allocations page: Initialize Minter dialog creates minter, row updates to "Minter Active"
• Allocations page: External toggle disabled when minter active

🤖 Generated with Claude Code