Make units column optional throughout source registration and SQL generation

- SQL generator no longer requires a units col; recode/clone/scale omit units
  expressions when none is configured in col_meta
- Source registration validation drops units from required roles (value + date
  are the only hard requirements)
- DELETE /api/sources/:id returns 409 when existing versions reference the source
- Setup.jsx surfaces the 409 error via flash instead of silently failing

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

lib/sql_generator.js

@@ -21,7 +21,6 @@ function generateSQL(source, colMeta) {
     const dateCol  = colMeta.find(c => c.role === 'date')?.cname;
 
     if (!valueCol) throw new Error('No value column defined in col_meta');
-    if (!unitsCol) throw new Error('No units column defined in col_meta');
     if (!dateCol)  throw new Error('No date column defined in col_meta');
     if (dims.length === 0) throw new Error('No dimension columns defined in col_meta');
 
@@ -171,14 +170,14 @@ ilog AS (
 )
 ,neg AS (
     INSERT INTO {{fc_table}} (${insertCols})
-    SELECT ${dimsJoined}, ${q(dateCol)}, ${effectiveValue ? `-${q(effectiveValue)}` : '0'}, ${effectiveUnits ? `-${q(effectiveUnits)}` : '0'},
+    SELECT ${dimsJoined}, ${q(dateCol)}, ${effectiveValue ? `-${q(effectiveValue)}` : '0'}${effectiveUnits ? `, -${q(effectiveUnits)}` : ''},
            'recode', (SELECT id FROM ilog), '{{pf_user}}', now()
     FROM src
     RETURNING *
 )
 ,ins AS (
     INSERT INTO {{fc_table}} (${insertCols})
-    SELECT {{set_clause}}, ${q(dateCol)}, ${effectiveValue ? q(effectiveValue) : '0'}, ${effectiveUnits ? q(effectiveUnits) : '0'},
+    SELECT {{set_clause}}, ${q(dateCol)}, ${effectiveValue ? q(effectiveValue) : '0'}${effectiveUnits ? `, ${q(effectiveUnits)}` : ''},
            'recode', (SELECT id FROM ilog), '{{pf_user}}', now()
     FROM src
     RETURNING *
@@ -199,8 +198,7 @@ ilog AS (
     SELECT
         {{set_clause}},
         ${q(dateCol)},
-        ${effectiveValue ? `round(${q(effectiveValue)} * {{scale_factor}}, 2)` : '0'},
-        ${effectiveUnits ? `round(${q(effectiveUnits)} * {{scale_factor}}, 5)` : '0'},
+        ${effectiveValue ? `round(${q(effectiveValue)} * {{scale_factor}}, 2)` : '0'}${effectiveUnits ? `,\n        round(${q(effectiveUnits)} * {{scale_factor}}, 5)` : ''},
         'clone', (SELECT id FROM ilog), '{{pf_user}}', now()
     FROM {{fc_table}}
     WHERE {{where_clause}}

routes/sources.js

@@ -143,7 +143,7 @@ module.exports = function(pool) {
             // validate required roles
             const colMeta = colResult.rows;
             const roles   = new Set(colMeta.map(c => c.role));
-            const missing = ['value', 'units', 'date'].filter(r => !roles.has(r));
+            const missing = ['value', 'date'].filter(r => !roles.has(r));
             if (missing.length > 0) {
                 return res.status(400).json({
                     error: `col_meta is missing required roles: ${missing.join(', ')}`
@@ -292,6 +292,9 @@ module.exports = function(pool) {
             res.json({ message: 'Source deregistered', source: result.rows[0] });
         } catch (err) {
             console.error(err);
+            if (err.code === '23001' || err.code === '23503') {
+                return res.status(409).json({ error: 'Source has existing versions — delete them first.' });
+            }
             res.status(500).json({ error: err.message });
         }
     });

ui/src/views/Setup.jsx

@@ -140,7 +140,12 @@ export default function Setup({ refreshSources }) {
   async function deleteSource(id, e) {
     e.stopPropagation()
     if (!confirm('Deregister this source? Existing forecast tables are not affected.')) return
-    await fetch(`/api/sources/${id}`, { method: 'DELETE' })
+    const res = await fetch(`/api/sources/${id}`, { method: 'DELETE' })
+    if (!res.ok) {
+      const data = await res.json().catch(() => ({}))
+      flash(data.error || 'Delete failed', 'err')
+      return
+    }
     if (selectedSource?.id === id) { setSelectedSource(null); setCols([]); setEditedCols([]) }
     loadSources()
   }