Add Parts section: consumable stock inventory (caps, resistors, etc.)

- New parts table with category, MPN, value, voltage, tolerance, power, mounting (THT/SMT), package, quantity, location
- /parts list (table view, category + mounting filters, colour-coded stock)
- /parts/new and /parts/[id]/edit with dynamic fields per category
- /parts/[id] detail with ± stock adjustment
- Sidebar nav entry and count badge
- Drizzle migration generated (run db:push to apply)

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

drizzle/migrations/meta/_journal.json

@@ -0,0 +1,13 @@
+{
+  "version": "7",
+  "dialect": "postgresql",
+  "entries": [
+    {
+      "idx": 0,
+      "version": "7",
+      "when": 1782725202288,
+      "tag": "0000_clear_sister_grimm",
+      "breakpoints": true
+    }
+  ]
+}