feat: initial FastAPI boilerplate setup

Set up Webber - multi-agent AI development system with:

- Domain-based project structure (src/domains/, src/shared/)
- BaseController pattern with lazy router instantiation
- Pydantic Settings configuration with env file support
- Logger decorator with temporal benchmarking and trace IDs
- UserProvider singleton for request-scoped context
- Custom exception hierarchy
- Health endpoints (/, /health)

Dependencies (CVE checked 2026-01-09):
- FastAPI 0.128.0, Starlette 0.50.0, Uvicorn 0.40.0
- Pydantic 2.12.4, PydanticAI 1.40.0
- All packages at latest safe versions

Placeholder domains for future implementation:
- agents/ (explore, plan, task)
- tools/ (file, shell, search)
- auth/ (tatlock integration)

Port: 8086 (per CONTAINERS.md allocation)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/domains/agents/README.md

@@ -0,0 +1,53 @@
+# Agents Domain
+
+This domain contains PydanticAI agent definitions and orchestration.
+
+## Structure
+
+```
+agents/
+├── router.py        # Agent routes (list, run)
+├── controller.py    # Agent orchestration logic
+├── schemas.py       # Request/response models
+│
+├── explore/         # Explore agent - codebase navigation
+│   ├── agent.py     # PydanticAI agent definition
+│   └── prompts.py   # System prompts
+│
+├── plan/            # Plan agent - implementation design
+│   ├── agent.py
+│   └── prompts.py
+│
+└── task/            # Task agent - execution
+    ├── agent.py
+    └── prompts.py
+```
+
+## PydanticAI Pattern
+
+```python
+from pydantic_ai import Agent
+from pydantic_ai.models.ollama import OllamaModel
+from src.shared.config import get_settings
+
+settings = get_settings()
+
+explore_agent = Agent(
+    OllamaModel(settings.ollama_agent_model, base_url=settings.ollama_url),
+    system_prompt='You are a code exploration assistant...',
+)
+
+@explore_agent.tool
+async def search_files(ctx, pattern: str) -> str:
+    """Search for files matching pattern."""
+    # Implementation uses tools from src/domains/tools/
+    pass
+```
+
+## Adding a New Agent
+
+1. Create a new directory under `agents/` (e.g., `agents/review/`)
+2. Create `agent.py` with PydanticAI Agent definition
+3. Create `prompts.py` with system prompts
+4. Register in `controller.py`
+5. Add tests in `tests/domains/test_agents/`