Add framework management with full i18n support

[neyec]

Summary

• Add ability to remove optional frameworks (UNDP, Environmental) and re-add them via the frameworks page — EU AI Act is fixed
• Backend endpoints: DELETE, POST, GET /available for framework CRUD
• Environmental Impact Framework is no longer seeded by default; it starts blank when added
• Full i18n: framework names, descriptions, and all reporting checklist items (titles, questions, tab labels) translated across en, es, fr, de
• Refactored Environmental and UNDP checklists from hardcoded English to the same translation pattern as EU AI Act
• Sidebar updates reactively when frameworks are added/removed
• Selected project now persists across page refreshes via localStorage
• Fixed fwName variable ordering bug in reporting page export

Test plan

• Delete UNDP framework → disappears from sidebar and reporting
• Click "Add Framework" → UNDP shows as available → add it → reappears
• EU AI Act has no delete button
• Switch language to es/fr/de → framework names, descriptions, and all checklist items are translated
• Environmental reporting page shows translated tab labels and questions
• Refresh the page → selected project is preserved
• Export PDF with translated framework name

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