[DISC-002] Persist discovery filter state in the URL

[chev0004]

Outline

Summary

Makes the URL the source of truth for the discovery page's filter, search, sort, tag, and pagination state, so a filtered view survives refresh, deep linking, and locale switches.

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Changes & Enhancements

• Type of Change:
  • Feature
  • Bugfix
  • Refactor
  • Chore
• Changes:
  • (discovery):
    • Add a URL-state module that serializes filter, search, sort, tag, and page state to query params and parses it back, omitting defaults and preserving unrelated params.
    • Hydrate the discovery controls from the URL on load and write state changes back with history.replaceState, keeping filtering client-side with no server refetch.
  • (navbar):
    • Carry the active query string across locale switches so changing language keeps the current filters.

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Page / App Changes

Affected Next.js Routes (Local):

• /[lang]

Before (Screenshot)

After (Screenshot)

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Component / Storybook Changes

Affected Storybook Components (Local):

Before (Screenshot)

After (Screenshot)

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Not Doing

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Other (Remarks)

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Checklists

• Code is well-documented (comments, JSDoc, etc.).
• Existing comments were updated as needed.
• No out-of-scope changes are included.
• Write TODO comments where future work is required.
• Removed unnecessary debug code (e.g., console.log, debugger).
• Self-reviewed and tested locally.