refactor(claude): Split autogpt_platform/CLAUDE.md into project-specific files (#11788)

Split `autogpt_platform/CLAUDE.md` into project-specific files, to make
the scope of the instructions clearer.

Also, some minor improvements:

- Change references to other Markdown files to @file/path.md syntax that
Claude recognizes
- Update ambiguous/incorrect/outdated instructions
- Remove trailing slashes
- Fix broken file path references in other docs (including comments)

docs/platform/contributing/oauth-integration-flow.md

@@ -25,7 +25,7 @@ This document focuses on the **API Integration OAuth flow** used for connecting
 ### 2. Backend API Trust Boundary
 - **Location**: Server-side FastAPI application
 - **Components**:
-  - Integration router (`/backend/backend/server/integrations/router.py`)
+  - Integration router (`/backend/backend/api/features/integrations/router.py`)
   - OAuth handlers (`/backend/backend/integrations/oauth/`)
   - Credentials store (`/backend/backend/integrations/credentials_store.py`)
 - **Trust Level**: Trusted - server-controlled environment

docs/platform/ollama.md

@@ -246,7 +246,7 @@ If you encounter any issues, verify that:
   ```bash
   ollama pull llama3.2
   ```
-- If using a custom model, ensure it's added to the model list in `backend/server/model.py`
+- If using a custom model, ensure it's added to the model list in `backend/api/model.py`
 
 #### Docker Issues
 - Ensure Docker daemon is running: