Feature/implement design system

[rosanyonghang]

• Extract features/issues and features/project into domain modules with slim pages
• Fix issue filter navigation bug preventing clearing/switching labels and search queries
• Sanitize query params in useProjectIssues hook to avoid 400 validation errors
• Split monolithic src/lib/i18n.ts into modular dictionaries and utils
• Add typed env validation via @t3-oss/env-nextjs in src/env.ts

[rosan-qsystems]

Resolved merge conflicts across member directory, profile details, project spotlight, and i18n dictionaries:

• Harmonized modular MemberDirectory and MemberProfileHero with removal of fabricated public data from main
• Restored official government affiliation badges and live statistics in ProjectSpotlightSection
• Synchronized English and Nepali dictionaries with new activity keys and updated footer navigation