Add DUBSAR Memory extension to community catalog

Add dubsar extension submitted by @kotnisofiane-bit to:
- extensions/catalog.community.json (alphabetical order)
- docs/community/extensions.md community extensions table

Closes #4130

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

docs/community/extensions.md

@@ -58,6 +58,7 @@ The following community-contributed extensions are available in [`catalog.commun
 | Data Model Diagram | Generates Mermaid ER diagrams from Spec Kit data models after planning | `docs` | Read+Write | [spec-kit-data-model-diagram](https://github.com/benizzio/spec-kit-data-model-diagram) |
 | DocGuard — CDD Enforcement | The only doc-integrity engine with an MCP server, SARIF/JUnit output, and a deterministic zero-LLM core. Validates, scores, and traces documentation against code — 27 validators, stable finding codes, adoption baseline for legacy repos, compliance-evidence reports, GitHub Action with PR annotations, spec-kit hooks. Pure Node.js, one pinned dep. | `docs` | Read+Write | [spec-kit-docguard](https://github.com/raccioly/docguard) |
 | Dotdog | Import GitHub Spec Kit artifacts into local knowledge graphs for validation, analysis, search, and MCP queries. | `docs` | Read+Write | [dotdog](https://github.com/specdog/dotdog) |
+| DUBSAR Memory | Local project memory for Spec Kit with explicit checkpoints, cross-session resume, and SHA-256 freshness for recorded specification, plan, and task references. | `visibility` | Read+Write | [dubsar-memory](https://github.com/kotnisofiane-bit/dubsar-memory) |
 | EARS Requirements Syntax | Author, lint, and convert requirements using EARS - the five industry-standard sentence patterns for unambiguous, testable requirements | `docs` | Read+Write | [spec-kit-ears](https://github.com/dhruv-15-03/spec-kit-ears) |
 | Extensify | Create and validate extensions and extension catalogs | `process` | Read+Write | [extensify](https://github.com/mnriem/spec-kit-extensions/tree/main/extensify) |
 | Figma Starter | Turns a Figma section's screens into per-screen spec.md files, an app-level user-stories.md, and a build-order.md, then hands off to /speckit.specify | `integration` | Read+Write | [spec-kit-figma-starter](https://github.com/wavemaker/spec-kit-figma-starter) |