The fluffy descriptions in Pathfinder are fluff; they serve to illustrate the mechanic, but they don't modify the mechanic. The only rules-relevant text is the mechanical text; in the case of Lunging Spell Touch (as with most feats), that's the Prerequisite(s) and the Benefit.
The relevant part of the feat's benefit is:
You can increase the reach of your spells’ melee touch attacks by 5 feet until the end of your turn by taking a –2 penalty to your AC until your next turn.
The Benefit section says nothing about "foes", just that you can increase the range of "Range: Touch". Is Cure Light Wounds a "Range: Touch" spell? Yes. Therefore, Lunging Spell Touch can modify it, and the caster can lunge to heal an ally.
Note that "Range: touch" implies a touch attack:
Touch
You must touch a creature or object to affect it. A touch spell that deals damage can score a critical hit just as a weapon can. A touch spell threatens a critical hit on a natural roll of 20 and deals double damage on a successful critical hit. You can touch up to 6 willing targets as part of the casting, but all targets of the spell must be touched in the same round that you finish casting the spell. ...
Since "Range: touch" spells can score critical hits, they must necessarily be attacks (and, that they're touch attacks is implied by being "touch" spells).
-- spell range description
Compare, say, Deadly Troupe Teamwork, which includes "foe" in the Benefit section:
When at least one ally who also has this feat is threatening a foe, you [gain bonuses]. You also gain [bonus on some] checks made against that foe.