docs(FN-007): add repository connection documentation

- Update development.md with Repository Connections section
- Document SSH key generation and provider adapter usage

docs/development.md

@@ -217,7 +217,7 @@ and local CLI operations evolve independently:
 Security rules for the package:
 - Credential models store **only** `encrypted_payload` — no plaintext `token` or `private_key` fields.
 - SSH private keys are encrypted before storage; the field uses `repr=False`.
-- Real encryption of the payload is deferred to FN-009; the current placeholder is base64-only.
+- SSH private keys are encrypted with Fernet before storage.
 
 ## Tool Spawn Workflow
 
@@ -324,6 +324,59 @@ When a tool instance is spawned:
 
 Before spawning, the system validates that all required secrets exist. If any are missing, the spawn fails with an error message listing the missing secrets.
 
+## Repository Connections
+
+### Overview
+
+The platform supports connecting Git repositories to projects with provider-independent authentication.
+
+### Architecture
+
+1. **Repository** (`apps/api/app/models/repository.py`):
+   - Stores repository metadata (name, git_url, provider_type, default_branch)
+   - Belongs to a project
+
+2. **Repository Connection** (`apps/api/app/models/repository_connection.py`):
+   - Links a repository to a Git provider with credentials
+   - Tracks connection status (pending, connected, error, disconnected)
+   - Supports SSH key authentication
+
+3. **Credential Storage** (`apps/api/app/git/credential_storage.py`):
+   - Database-backed storage for encrypted credentials
+   - Uses Fernet encryption for payload
+   - Supports access tokens and SSH keys
+
+4. **Provider Adapters** (`apps/api/app/git/providers/`):
+   - GitHubAdapter and GitLabAdapter with URL parsing
+   - Extensible for other providers (Gitea, Forgejo)
+
+5. **SSH Key Lifecycle** (`apps/api/app/git/ssh_key.py`):
+   - Ed25519 key pair generation
+   - Fernet-encrypted private key storage
+   - Public key available for deploy key registration
+
+### API Endpoints
+
+- `POST /projects/{id}/repositories` — Add repository
+- `GET /projects/{id}/repositories` — List repositories
+- `DELETE /projects/{id}/repositories/{id}` — Remove repository
+- `POST /projects/{id}/repository-connections` — Create connection
+- `GET /projects/{id}/repository-connections` — List connections
+- `DELETE /projects/{id}/repository-connections/{id}` — Remove connection
+- `POST /projects/{id}/repository-connections/{id}/ssh-key` — Generate SSH key
+- `POST /projects/{id}/repository-connections/{id}/validate` — Validate connection
+
+### Frontend
+
+- `/repositories` — Repository list and creation
+- `/projects/{id}/repositories/{id}` — Repository detail with connections
+
+### Git Operations
+
+Local Git operations are supported via subprocess:
+- Clone, fetch, push with credential-aware subprocess
+- Working tree status (branch, clean, untracked, modified, staged, deleted)
+
 ## OpenCode Tool
 
 ### Overview