A typo on my part..I meant 2505.
The 3.3v was because I was't to use as less power as possible.
For the least amount of power during a grid power outage, just unplug the supply for the PIC/light-switch, the manual switch will still work...unless the PIC is doing something else. If it were portable or going to Mars it might be worth the small savings in power.
And, you don' need the optocoupler on the output of the PIC, the relay isolates it.
I attached two schematics that might work.
DX is an anti-flyback diode to protect the transistor from the relay's reverse voltage spike when it de-energizes. Best practice is to include it.
In the both schematics the PIC output opto-coupler is replaced by a transistor. Ry is added as a pull-up on the PIC's input. It may not be necessary.
In the first schematic R3's value is still unknown, based on the PS2501's gain. And, by moving the LED to the collector you take full advantage of the coupler's transfer current gain.
The second schematic uses my diode configuration. Again, the diodes's current ratings depend on the IL wattage. It looks the 1N4001s will work.
Ken