Make BCN, SOL, PDP symbols consistent: same viewBox, font, and size

All three now use identical 20x20 viewBox, 19x19 rect, font-size 8,
centered text with dominant-baseline="central". Updated symbol defs
to match the new 20x20 dimensions.

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

svelte-app/src/lib/symbols.ts

@@ -54,12 +54,12 @@ export const SYMBOLS: SymbolDef[] = [
   { id: 'package_release_v', name: 'Package Release (V)', file: '/symbols/package_release.svg', w: 20, h: 20, defaultRotation: 90, group: 'Controls' },
   { id: 'beacon',         name: 'Beacon',            file: '/symbols/beacon.svg',              w: 20, h: 20, group: 'Controls' },
   { id: 'beacon_v',       name: 'Beacon (V)',        file: '/symbols/beacon.svg',              w: 20, h: 20, defaultRotation: 90, group: 'Controls' },
-  { id: 'solenoid',       name: '[SOL]',             file: '/symbols/solenoid.svg',            w: 30, h: 20, group: 'Controls' },
+  { id: 'solenoid',       name: '[SOL]',             file: '/symbols/solenoid.svg',            w: 20, h: 20, group: 'Controls' },
-  { id: 'solenoid_v',     name: '[SOL] (V)',         file: '/symbols/solenoid.svg',            w: 30, h: 20, defaultRotation: 90, group: 'Controls' },
+  { id: 'solenoid_v',     name: '[SOL] (V)',         file: '/symbols/solenoid.svg',            w: 20, h: 20, defaultRotation: 90, group: 'Controls' },
 
   // --- Other ---
-  { id: 'pdp',            name: 'PDP',               file: '/symbols/pdp.svg',                 w: 30,  h: 20, group: 'Other' },
+  { id: 'pdp',            name: 'PDP',               file: '/symbols/pdp.svg',                 w: 20,  h: 20, group: 'Other' },
-  { id: 'pdp_v',          name: 'PDP (V)',           file: '/symbols/pdp.svg',                 w: 30,  h: 20, defaultRotation: 90, group: 'Other' },
+  { id: 'pdp_v',          name: 'PDP (V)',           file: '/symbols/pdp.svg',                 w: 20,  h: 20, defaultRotation: 90, group: 'Other' },
   { id: 'dpm',            name: 'DPM',               file: '/symbols/dpm.svg',                 w: 35,  h: 20, group: 'Other' },
   { id: 'dpm_v',          name: 'DPM (V)',           file: '/symbols/dpm.svg',                 w: 35,  h: 20, defaultRotation: 90, group: 'Other' },
   { id: 'mcm',            name: 'MCM',               file: '/symbols/mcm.svg',                 w: 60,  h: 20, group: 'Other' },