docs: add finance app overview and roadmap to README

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

README.md

@@ -1,3 +1,86 @@
 # k3s Home Lab
 
 - author: @GoncaloRodri
+
+---
+
+## Finance App
+
+A self-hosted personal finance dashboard running on k3s. Tracks transactions, budgets, and investments — with the goal of becoming a full financial co-pilot.
+
+### Current features
+
+- Import bank transactions via CSV (CGD, Trade Republic, generic)
+- Categorise transactions with auto-categorisation and colour-coded badges
+- Monthly budget tracking with progress bars (over-budget alerts)
+- Dashboard with income vs expense split and 90-day balance trend
+- Monthly reports (stacked bar chart, 12-month breakdown)
+- Spending projections based on 6-month average
+- Investment portfolio with live prices via Yahoo Finance and a 3-D allocation chart
+- Dark / light mode with system preference detection
+- Read-only sharing between users
+
+---
+
+## Roadmap
+
+The main goal is to evolve from a **ledger** (records what happened) into a **financial co-pilot** (tells you what to do next, based on where you want to end up).
+
+### Phase 1 — Disposable income number *(next)*
+
+A single, always-visible number: **"You have €X to spend freely this month."**
+
+Calculated as: `Income − fixed expenses − goal contributions − category budgets`
+
+- Auto-detect fixed/recurring expenses from transaction history (rent, subscriptions, utilities)
+- Separate fixed costs from variable spend so budgets only cover what you can actually control
+- Savings rate trend (% of income saved each month)
+
+---
+
+### Phase 2 — Goals: explore mode
+
+Before committing to a financial goal, plan it first.
+
+- Goal types: **one-off purchase** (Nintendo Switch, laptop, holiday), **deposit / down-payment** (house, apartment), **emergency fund** (auto-sized to N months of your average spend), **recurring investment** (links to the portfolio)
+- Input: target amount + deadline
+- Output: monthly contribution needed, impact on disposable income, months to target at current savings rate
+- No commitment required — explore as many scenarios as you want
+
+---
+
+### Phase 3 — Goals: commit + plan
+
+- Committed goals generate a monthly "reservation" deducted from your disposable income
+- Conflict detection: "you can't fund both the Switch by June and the house deposit by 2028 at this savings rate"
+- Goal progress tracking over time
+
+---
+
+### Phase 4 — Net worth
+
+- Cash accounts + portfolio market value − credit card balances = net worth
+- Historical net worth chart (all data already exists, just needs aggregation)
+
+---
+
+### Phase 5 — "What if" simulator + savings rate
+
+- Drag a slider for income change, a one-off expense, or a new goal — see how it ripples through disposable income and goal timelines
+- Savings rate history and trend once several months of goal data exist
+
+---
+
+### Phase 6 — Alerts and nudges
+
+- "You've spent 80% of your Food budget and it's only the 15th"
+- "You're on track to miss your Switch goal by 2 months"
+- Delivered as dashboard banners initially, push notifications or email later
+
+---
+
+### Future / backlog
+
+- **Household mode** — merge incomes and goals for couples planning together (extends the existing sharing feature)
+- **Automatic transaction import** — scheduled CSV fetch or open banking integration
+- **Tax summary** — annual income, investment gains, and deductible expenses export