Add COUNTER type with auto-increment and IsNegative field

COUNTER type:
- Only accepts integer values (rejects decimals)
- Auto-increment behavior: each mark adds to existing value
- Supports decrement via negative values (e.g., -2)
- Enforces minimum value of 0 (never negative)
- Default increment is 1 if no value provided

VALUE type:
- Accepts decimal values
- Replaces value (no auto-increment)

IsNegative field:
- New boolean field on Habit entity
- Persisted in database (is_negative column)
- Available in all DTOs and HTTP responses
- Marks habits as "negative" (e.g., candy consumption)

Examples:
- COUNTER: 5 + (-2) = 3, 2 + (-3) = 0, 0 + (-1) = 0
- VALUE: 5000 → 12000 = 12000 (replacement)

go.mod

@@ -13,6 +13,22 @@ require (
 	github.com/joho/godotenv v1.5.1
 	github.com/mattn/go-sqlite3 v1.14.32
 	github.com/swaggo/http-swagger v1.3.4
-	github.com/swaggo/swag v1.16.4
 	golang.org/x/crypto v0.45.0
 )
+
+require (
+	github.com/KyleBanks/depth v1.2.1 // indirect
+	github.com/cespare/xxhash/v2 v2.1.2 // indirect
+	github.com/go-openapi/jsonpointer v0.19.5 // indirect
+	github.com/go-openapi/jsonreference v0.20.0 // indirect
+	github.com/go-openapi/spec v0.20.6 // indirect
+	github.com/go-openapi/swag v0.19.15 // indirect
+	github.com/josharian/intern v1.0.0 // indirect
+	github.com/mailru/easyjson v0.7.6 // indirect
+	github.com/swaggo/files v0.0.0-20220610200504-28940afbdbfe // indirect
+	github.com/swaggo/swag v1.16.4 // indirect
+	golang.org/x/net v0.47.0 // indirect
+	golang.org/x/sys v0.38.0 // indirect
+	golang.org/x/tools v0.7.0 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+)