feat(catalog): add Gemma 4 12B/QAT entries and RTX 3050 bandwidth (#4728)

Add official Gemma 4 12B-it plus QAT-INT4/INT8 catalog entries (with their
GGUF sources), QAT quantization support across the quant tables and the
prequantized-prefix list, and the missing RTX 3050 / 3050 Ti memory
bandwidth so speed estimates stop falling back to the generic cuda value.

tests/test_hwfit_gemma4_12b.py

@@ -0,0 +1,51 @@
+from services.hwfit.fit import rank_models
+from services.hwfit.models import get_models, is_prequantized
+
+
+def _8gb_vram_system():
+    return {
+        "has_gpu": True,
+        "backend": "cuda",
+        "gpu_name": "NVIDIA GeForce RTX 4060",
+        "gpu_vram_gb": 8.0,
+        "gpu_count": 1,
+        "available_ram_gb": 32.0,
+        "total_ram_gb": 32.0,
+    }
+
+
+def test_gemma4_12b_in_catalog():
+    catalog = {m["name"]: m for m in get_models()}
+    assert "google/gemma-4-12B-it" in catalog, "gemma-4-12B-it missing from catalog"
+
+
+def test_gemma4_12b_has_gguf_source():
+    catalog = {m["name"]: m for m in get_models()}
+    entry = catalog["google/gemma-4-12B-it"]
+    assert entry.get("gguf_sources"), "gemma-4-12B-it has no gguf_sources"
+    repos = [s["repo"] for s in entry["gguf_sources"]]
+    assert "unsloth/gemma-4-12B-it-GGUF" in repos
+
+
+def test_gemma4_12b_rank_models_returns_it_for_8gb_vram():
+    results = rank_models(_8gb_vram_system(), search="gemma-4-12B-it", limit=20)
+    names = [r["name"] for r in results]
+    assert "google/gemma-4-12B-it" in names, "rank_models did not return gemma-4-12B-it for 8 GB VRAM"
+
+
+def test_gemma4_12b_qat_entries_in_catalog():
+    catalog = {m["name"]: m for m in get_models()}
+    assert "google/gemma-4-12B-it-qat-int4" in catalog
+    assert "google/gemma-4-12B-it-qat-int8" in catalog
+
+
+def test_gemma4_12b_qat_entries_are_prequantized():
+    catalog = {m["name"]: m for m in get_models()}
+    assert is_prequantized(catalog["google/gemma-4-12B-it-qat-int4"])
+    assert is_prequantized(catalog["google/gemma-4-12B-it-qat-int8"])
+
+
+def test_gemma4_12b_qat_entries_have_no_gguf():
+    catalog = {m["name"]: m for m in get_models()}
+    assert catalog["google/gemma-4-12B-it-qat-int4"]["gguf_sources"] == []
+    assert catalog["google/gemma-4-12B-it-qat-int8"]["gguf_sources"] == []