feat: Migrate MaterialDimensions from TPH to TPC and add Alro catalog seeding

Switch MaterialDimensions inheritance from TPH (single table with discriminator)
to TPC (table per concrete type) with individual tables per shape. Add Swagger
for dev API exploration, expand SeedController with export/import endpoints and
Alro catalog JSON dataset, and include Python scraper for Alro catalog PDFs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/AlroCatalog/SCRAPE_PLAN.md

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+# Alro Steel SmartGrid Scraper — Remaining Steps
+
+## Status: Script is READY TO RUN
+
+The scraper at `scripts/AlroCatalog/scrape_alro.py` is complete and tested. Discovery mode confirmed it works correctly against the live site.
+
+## What's Done
+1. Script written with correct ASP.NET control IDs (discovered via `--discover` mode)
+2. Level 1 (main grid) navigation: working
+3. Level 2 (popup grid) navigation: working
+4. Level 3 (dims panel) scraping: working — uses cascading dropdowns `ddlDimA` → `ddlDimB` → `ddlDimC` → `ddlLength`
+5. Grade filter: 11 common grades (A-36, 1018, 1045, 1144, 12L14, etc.)
+6. Size string normalization: "1-1/2\"" matches O'Neal format
+7. Progress save/resume: working
+8. Discovery mode verified: A-36 Round bars → 27 sizes, 80 items (lengths include "20 FT", "Custom Cut List", "Drop/Remnant" — non-stock entries filtered out in catalog builder)
+
+## Remaining Steps
+
+### Step 1: Run the full scrape
+```bash
+cd C:\Users\aisaacs\Desktop\Projects\CutList
+python scripts/AlroCatalog/scrape_alro.py
+```
+- This scrapes all 3 categories (Bars, Pipe/Tube, Structural) for 11 filtered grades
+- Takes ~30-60 minutes (cascading dropdown selections with 1.5s delay each)
+- Progress saved incrementally to `scripts/AlroCatalog/alro-scrape-progress.json`
+- If interrupted, resume with `python scripts/AlroCatalog/scrape_alro.py --resume`
+- To scrape ALL grades: `python scripts/AlroCatalog/scrape_alro.py --all-grades`
+
+### Step 2: Review output
+- Output: `CutList.Web/Data/SeedData/alro-catalog.json`
+- Verify material counts, shapes, sizes
+- Spot-check dimensions against myalro.com
+- Compare shape coverage to O'Neal catalog
+
+### Step 3: Post-scrape adjustments (if needed)
+
+**Dimension mapping for Structural/Pipe shapes**: The `build_size_and_dims()` function handles all shapes but Structural (Angle, Channel, Beam) and Pipe/Tube shapes haven't been tested live yet. After scraping, check the screenshots in `scripts/AlroCatalog/screenshots/` to verify dimension mapping. The first item of each new shape gets a screenshot + HTML dump.
+
+**Known dimension mapping assumptions:**
+- Angle: DimA = leg size, DimB = thickness → `"leg1 x leg2 x thickness"` (assumes equal legs)
+- Channel: DimA = height, DimB = flange → needs verification
+- IBeam: DimA = depth, DimB = weight/ft → `"W{depth} x {wt}"`
+- SquareTube: DimA = size, DimB = wall
+- RectTube: DimA = width, DimB = height, DimC = wall
+- RoundTube: DimA = OD, DimB = wall
+- Pipe: DimA = NPS, DimB = schedule
+
+**If dimension mapping is wrong for a shape**: Edit the `build_size_and_dims()` function in `scrape_alro.py` and re-run just the catalog builder:
+```python
+python -c "
+import json
+from scripts.AlroCatalog.scrape_alro import build_catalog
+data = json.load(open('scripts/AlroCatalog/alro-scrape-progress.json'))
+catalog = build_catalog(data['items'])
+json.dump(catalog, open('CutList.Web/Data/SeedData/alro-catalog.json', 'w'), indent=2)
+"
+```
+
+### Step 4: Part numbers (optional future enhancement)
+The current scraper captures sizes and lengths but NOT part numbers. To get part numbers, the script would need to:
+1. Select DimA + DimB + Length
+2. Click the "Next >" button (`btnSearch`)
+3. Capture part number from the results panel
+4. Click Back
+
+This adds significant time per item. The catalog works without part numbers — the supplierOfferings have empty partNumber/supplierDescription fields.
+
+## Key Files
+| File | Purpose |
+|------|---------|
+| `scripts/AlroCatalog/scrape_alro.py` | The scraper script |
+| `scripts/AlroCatalog/alro-scrape-progress.json` | Incremental progress (resume support) |
+| `scripts/AlroCatalog/screenshots/` | Discovery HTML/screenshots per shape |
+| `CutList.Web/Data/SeedData/alro-catalog.json` | Final output (same schema as oneals-catalog.json) |
+| `CutList.Web/Data/SeedData/oneals-catalog.json` | Reference format |
+
+## Grade Filter (editable in script)
+Located at line ~50 in `scrape_alro.py`. Current filter:
+- A-36, 1018 CF, 1018 HR, 1044 HR, 1045 CF, 1045 HR, 1045 TG&P
+- 1144 CF, 1144 HR, 12L14 CF, A311/Stressproof
+
+To add/remove grades, edit the `GRADE_FILTER` set in the script.