SaaS spend growth & shadow IT detection

# SaaS spend growth analysis

## Purpose
Map all SaaS spend (monthly/annual subscriptions), identify unnegotiated price increases, detect new subscriptions (shadow IT), and calculate the total software cost.

## Instructions

### Step 1 — Identify SaaS spend
```
Call spendesk_analyze_spend with:
  - groupBy: supplier
  - Filter by category: "SaaS", "Software", "Logiciels", "IT", "Subscriptions"
    (use the categories available in your Spendesk account)
  - Period: last 12 months

OR call get_payables with:
  - payableType: subscription (if available)
  - Last 12 months

For each SaaS expense: supplier, amount, frequency (monthly/annual), date.
```

### Step 2 — Calculate the normalized annual cost per tool
```
For each identified SaaS supplier:
  If regular monthly payments: annual cost = monthly average × 12
  If annual payments: annual cost = renewal amount
  If irregular: total of the last 12 months

Rank by descending annual cost → get the Top 20 SaaS tools.
```

### Step 3 — Analyze year-over-year growth
```
Compare for each SaaS tool:
  Average monthly cost over the last 6 months (recent period)
  vs
  Average monthly cost over the previous 6 months (prior period)

Growth = (recent period - prior period) / prior period × 100

Flag:
  🔴 Increase > 30%: likely price increase → to renegotiate
  🟡 Increase 10-30%: to monitor
  🟢 Stable or decrease: normal
```

### Step 4 — Detect shadow IT
```
For suppliers that appeared ONLY in the last 3 months:
  List the new subscriptions
  For each new one: supplier name, monthly amount, first payment date
  Categorize: known market tool? Likely business use?

Shadow IT = subscriptions taken out without central IT/Finance validation
```

### Step 5 — SaaS report
```
Present:
1. Top 20 SaaS tools by annual cost (table with supplier, annual cost, growth)

2. Price increase alerts:
   🔴 Tool | Old monthly cost | New monthly cost | Increase (%)

3. Shadow IT detected:
   Tool | First payment | Monthly cost | Cost center

4. KPIs:
   Total annualized SaaS: X€
   Growth vs last year: +X%
   Number of active SaaS tools: X
   SaaS cost per employee: X€/month (if get_users available)
```

## Points of attention
- SaaS spend categorization depends on the quality of categories in Spendesk
- Some tools are paid via virtual card (not visible via get_payables)
- Annual renewals create spikes in certain months — normalize over 12 months

## Example prompts
- "What is our total SaaS spend and how has it evolved?"
- "Are there any subscriptions that have increased without me knowing?"
- "List all new SaaS tools that appeared in the last 3 months"