feat: add generic Value[T] base class for value objects

- Create Value[T] (frozen dataclass + ABC + Generic) in domain/framework/
- Migrate ClassifiedAdTitle and ClassifiedAdText to inherit Value[str]
- Standardize all value access via .value instead of type-specific fields

.agent/current-plan.md

@@ -1,18 +1,45 @@
-# Plan: Add FastAPI to the Project
+# Plan: Value Object Base Class
 
 ## Goal
-Add FastAPI as the web framework with a minimal health check endpoint.
+Create a generic `Value[T]` base class in the framework layer. All value objects standardize on `.value` access via inheritance.
 
-## Changes
+## Design
 
-### 1. Dependencies
-- Add `fastapi` and `uvicorn[standard]` to `pyproject.toml` under `[project.dependencies]`
-- Install dependencies into the virtual environment
+### `Value[T]` base class (`domain/framework/value.py`)
+```python
+@dataclass(frozen=True)
+class Value(ABC, Generic[T]):
+    value: T
+```
 
-### 2. Application Entry Point
-- Create `main.py` with a FastAPI app instance
-- Add a health check endpoint (`GET /`) that returns `{"status": "ok"}`
+- Frozen dataclass → immutability + structural equality (core Value Object semantics)
+- `Generic[T]` → type-safe `.value` access in subclasses (e.g., `Value[str]`)
+- `ABC` → mirrors the `Entity` pattern
+
+### Subclasses
+- `ClassifiedAdTitle(Value[str])` — drops `title: str`, inherits `value: T` bound to `str`
+- `ClassifiedAdText(Value[str])` — drops `text: str`, inherits `value: T` bound to `str`
+
+### Ripple effects
+Every `.title` / `.text` reference on these objects becomes `.value`:
+- `classified_ad.py` — `self.title.title` → `self.title.value`, construction calls, method bodies
+- Tests — assertions, constructions, equality checks
+
+## Files changed
+| File | Change |
+|------|--------|
+| `domain/framework/value.py` | New — `Value[T]` base class |
+| `domain/framework/__init__.py` | Add `Value` re-export |
+| `domain/marketplace/classified_ad_title.py` | Inherit `Value[str]`, rename field |
+| `domain/marketplace/classified_ad_text.py` | Inherit `Value[str]`, rename field |
+| `domain/marketplace/classified_ad.py` | Update `.title`/`.text` refs → `.value` |
+| `tests/test_classified_ad_title.py` | Update refs |
+| `tests/test_classified_ad_text.py` | Update refs |
+| `tests/test_classified_ad.py` | Update refs |
+
+## Not in scope
+`ClassifiedAdId`, `UserId`, `Money`, `Price` — stay as-is.
 
 ## Verification
-- `pytest tests/` — all tests pass
-- `uvicorn main:app --reload` — server starts and health endpoint responds
+- `pytest tests/` — all 63 tests pass
+- `ruff check .` && `ruff format --check .` — clean