Canonicalize all community navigation under `/communities`

[Caneryy]

Planning

• Plan ID: H1
• Depends on: Consolidate the three community registry models into one adapter #248 (H2)
• PRD alignment: FR-1; UJ-1–UJ-4

Problem

The app currently owns behavior in three route families: /communities/**, /community/**, and /proposals/**. Users can enter different implementations of the same product journey, and contributors must update multiple route trees.

Scope

Use /communities, /communities/create, /communities/[id], /communities/[id]/proposals, and /communities/[id]/proposals/[proposalId] as canonical destinations. Convert singular and global legacy pages into thin redirects that preserve relevant query parameters. Update all internal links, breadcrumbs, navigation, component tests, route tests, E2E specs, and current docs.

Mechanical recipe

1. Add one route-builder module with typed helpers.
2. Replace hard-coded community/proposal paths with those helpers.
3. Replace legacy page bodies with redirects.
4. Update test expectations and documentation links.

Acceptance criteria

• No production component hard-codes a primary /community or global /proposals destination.
• Legacy URLs redirect to the equivalent canonical URL without losing identifiers or query parameters.
• Canonical route tests and Playwright navigation flows pass.

Verification

npm run lint && npm run typecheck && npm test && npm run test:e2e:ci

[emrekayat]

can ı look at it?

[grantfox-oss]

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Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #247)
2. Your PR will be reviewed by the stolla-labs maintainers

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