Restore accidentally removed files, a few additional import/calculation fixes

inventory-server/migrations/001_create_import_sessions.sql

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+-- Migration: Create import_sessions table
+-- Run this against your PostgreSQL database
+
+CREATE TABLE IF NOT EXISTS import_sessions (
+  id SERIAL PRIMARY KEY,
+  user_id INTEGER NOT NULL,
+  name VARCHAR(255),                    -- NULL for unnamed/autosave sessions
+  current_step VARCHAR(50) NOT NULL,    -- 'validation' | 'imageUpload'
+  data JSONB NOT NULL,                  -- Product rows
+  product_images JSONB,                 -- Image assignments
+  global_selections JSONB,              -- Supplier, company, line, subline
+  validation_state JSONB,               -- Errors, UPC status, generated item numbers
+  created_at TIMESTAMP DEFAULT NOW(),
+  updated_at TIMESTAMP DEFAULT NOW()
+);
+
+-- Ensure only one unnamed session per user (autosave slot)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_unnamed_session_per_user
+  ON import_sessions (user_id)
+  WHERE name IS NULL;
+
+-- Index for fast user lookups
+CREATE INDEX IF NOT EXISTS idx_import_sessions_user_id
+  ON import_sessions (user_id);
+
+-- Add comment for documentation
+COMMENT ON TABLE import_sessions IS 'Stores in-progress product import sessions for users';
+COMMENT ON COLUMN import_sessions.name IS 'Session name - NULL indicates the single unnamed/autosave session per user';
+COMMENT ON COLUMN import_sessions.current_step IS 'Which step the user was on: validation or imageUpload';

inventory-server/migrations/002_ai_prompts_extensible_types.sql

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+-- Migration: Make AI prompts extensible with is_singleton column
+-- Date: 2024-01-19
+-- Description: Removes hardcoded prompt_type CHECK constraint, adds is_singleton column
+--              for dynamic uniqueness enforcement, and creates appropriate indexes.
+
+-- 1. Drop the old CHECK constraints on prompt_type (allows any string value now)
+ALTER TABLE ai_prompts DROP CONSTRAINT IF EXISTS ai_prompts_prompt_type_check;
+ALTER TABLE ai_prompts DROP CONSTRAINT IF EXISTS company_required_for_specific;
+
+-- 2. Add is_singleton column (defaults to true for backwards compatibility)
+ALTER TABLE ai_prompts ADD COLUMN IF NOT EXISTS is_singleton BOOLEAN NOT NULL DEFAULT true;
+
+-- 3. Drop ALL old unique constraints and indexes (cleanup)
+-- Some were created as CONSTRAINTS (via ADD CONSTRAINT), others as standalone indexes
+-- Must drop constraints first, then remaining standalone indexes
+
+-- Drop constraints (these also remove their backing indexes)
+ALTER TABLE ai_prompts DROP CONSTRAINT IF EXISTS unique_company_prompt;
+ALTER TABLE ai_prompts DROP CONSTRAINT IF EXISTS idx_unique_general_prompt;
+ALTER TABLE ai_prompts DROP CONSTRAINT IF EXISTS idx_unique_system_prompt;
+
+-- Drop standalone indexes (IF EXISTS handles cases where they don't exist)
+DROP INDEX IF EXISTS idx_unique_general_prompt;
+DROP INDEX IF EXISTS idx_unique_system_prompt;
+DROP INDEX IF EXISTS idx_unique_name_validation_system;
+DROP INDEX IF EXISTS idx_unique_name_validation_general;
+DROP INDEX IF EXISTS idx_unique_description_validation_system;
+DROP INDEX IF EXISTS idx_unique_description_validation_general;
+DROP INDEX IF EXISTS idx_unique_sanity_check_system;
+DROP INDEX IF EXISTS idx_unique_sanity_check_general;
+DROP INDEX IF EXISTS idx_unique_bulk_validation_system;
+DROP INDEX IF EXISTS idx_unique_bulk_validation_general;
+DROP INDEX IF EXISTS idx_unique_name_validation_company;
+DROP INDEX IF EXISTS idx_unique_description_validation_company;
+DROP INDEX IF EXISTS idx_unique_bulk_validation_company;
+
+-- 4. Create new partial unique indexes based on is_singleton
+-- For singleton types WITHOUT company (only one per prompt_type)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_singleton_no_company
+  ON ai_prompts (prompt_type)
+  WHERE is_singleton = true AND company IS NULL;
+
+-- For singleton types WITH company (only one per prompt_type + company combination)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_singleton_with_company
+  ON ai_prompts (prompt_type, company)
+  WHERE is_singleton = true AND company IS NOT NULL;
+
+-- 5. Add index for fast lookups by type
+CREATE INDEX IF NOT EXISTS idx_prompt_type ON ai_prompts (prompt_type);
+
+-- NOTE: After running this migration, you should:
+-- 1. Delete existing prompts with old types (general, system, company_specific)
+-- 2. Create new prompts with the new type naming convention:
+--    - name_validation_system, name_validation_general, name_validation_company_specific
+--    - description_validation_system, description_validation_general, description_validation_company_specific
+--    - sanity_check_system, sanity_check_general
+--    - bulk_validation_system, bulk_validation_general, bulk_validation_company_specific