Expose DeduplicateInitializersPass in common passes module (#99)

This PR exposes the `DeduplicateInitializersPass` in the
`onnx_ir.passes.common` module by adding it to the `__all__` list and
importing it in the module's `__init__.py`.

## Changes Made

- Added `"DeduplicateInitializersPass"` to the `__all__` list in
alphabetical order
- Added import statement: `from
onnx_ir.passes.common.initializer_deduplication import
(DeduplicateInitializersPass,)`

## Before
```python
# This would fail with ImportError
from onnx_ir.passes.common import DeduplicateInitializersPass

# Users had to import directly from the submodule
from onnx_ir.passes.common.initializer_deduplication import DeduplicateInitializersPass
```

## After  
```python
# Now works as expected
from onnx_ir.passes.common import DeduplicateInitializersPass

# Pass can be used immediately
pass_instance = DeduplicateInitializersPass()
result = pass_instance(model)
```

The change follows the existing pattern used by other passes in the
module and maintains alphabetical ordering in both the `__all__` list
and import statements.

Fixes #98.

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Author: Copilot

src/onnx_ir/passes/common/__init__.py

@@ -6,6 +6,7 @@
     "CheckerPass",
     "ClearMetadataAndDocStringPass",
     "CommonSubexpressionEliminationPass",
+    "DeduplicateInitializersPass",
     "InlinePass",
     "LiftConstantsToInitializersPass",
     "LiftSubgraphInitializersToMainGraphPass",
@@ -29,6 +30,9 @@
     LiftSubgraphInitializersToMainGraphPass,
     RemoveInitializersFromInputsPass,
 )
+from onnx_ir.passes.common.initializer_deduplication import (
+    DeduplicateInitializersPass,
+)
 from onnx_ir.passes.common.inliner import InlinePass
 from onnx_ir.passes.common.onnx_checker import CheckerPass
 from onnx_ir.passes.common.shape_inference import ShapeInferencePass