[codex] improve search and filter controls

[Sean-Kenneth-Doherty]

Summary

• Add decorative search and filter SVG icons to the project list controls.
• Add left padding and responsive icon positioning so control text does not overlap the icons.
• Hide the decorative icons from assistive technology.
• Clarify the control labels as Search projects and Filter projects by tag.
• Dedupe filter dropdown tags case-insensitively so repeated values like GitHub/Github and TypeScript/Typescript only render once.

Addresses #454.
Contributes to #347.

Validation

• pnpm build
• Confirmed rendered dist/index.html has the updated input/select aria-label values
• Confirmed the old aria-labelledby="tag-selector-container" reference is gone
• Node check against built dist/index.html confirmed 305 filter options and no duplicate option values
• Source data check showed 39 case-only duplicate tag options removed
• git diff --check

[Sean-Kenneth-Doherty]

Withdrawing this to keep the contribution queue focused on the highest-signal fixes. I opened too many small slices here, and this one is less important than the concrete broken-link, security, workflow, rendering, and accessibility fixes that remain open.