refactor: consolidate AI analyzers into shared lib/ai module and add journal entry reversal columns

Extract shared vision/document analysis logic into lib/ai (vision-client, document-analyzer,
image preprocessing, validation helpers), simplifying invoice-analyzer, receipt-analyzer, and
document classifier. Add migration 046 for journal entry reversal/correction link columns
(reversed_by_id, reverses_id, correction_of_id) required by storno service. Update extension
components and shared UI.

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

supabase/migrations/20240101000046_add_journal_entry_reversal_columns.sql

@@ -0,0 +1,21 @@
+-- Add storno/correction link columns to journal_entries
+-- These are required for ändringsverifikationer (correction entries) per BFL 5 kap.
+-- The reverseEntry() and correctEntry() functions in engine.ts / storno-service.ts
+-- depend on these columns to create bidirectional links between entries.
+
+-- Link to storno entry that reversed this entry
+ALTER TABLE public.journal_entries
+  ADD COLUMN IF NOT EXISTS reversed_by_id uuid REFERENCES public.journal_entries(id) ON DELETE SET NULL;
+
+-- Link to the original entry that this storno reverses
+ALTER TABLE public.journal_entries
+  ADD COLUMN IF NOT EXISTS reverses_id uuid REFERENCES public.journal_entries(id) ON DELETE SET NULL;
+
+-- Link to the original entry in a correction chain (storno + new correct entry)
+ALTER TABLE public.journal_entries
+  ADD COLUMN IF NOT EXISTS correction_of_id uuid REFERENCES public.journal_entries(id) ON DELETE SET NULL;
+
+-- Indexes for FK lookups
+CREATE INDEX IF NOT EXISTS idx_journal_entries_reversed_by_id ON public.journal_entries (reversed_by_id);
+CREATE INDEX IF NOT EXISTS idx_journal_entries_reverses_id ON public.journal_entries (reverses_id);
+CREATE INDEX IF NOT EXISTS idx_journal_entries_correction_of_id ON public.journal_entries (correction_of_id);